Math Homework Help?

I dont get how too do this math :[





2/3 - (-4/5)





11 - (-10)





Evaluate x - y - z When X= 10.5,Y= 3.8, C


Z= 1-7





Evaluate a - (b - c) When A= -2,B= -3, C= 1/4





Solve For C: E= C-45





Solve For Y: 180 -Y = x

Math Homework Help?
ok, for most of these just realize that two minus signs in a row are the same as a plus sign





(2/3) - (-4/5) = 2/3+4/5 = 10/15+12/15 = 22/15





11-(-10) = 11+10 = 21





x-y-z ===%26gt; (10.5)-(3.8)-(1-7) = (10.5)-(3.8)-(-6)


10.5-3.8+6 = 12.7





a-(b-c) ===%26gt; (-2)-[(-3)-(.25)] = -2-(-3-.25)





-2-(-3.25) = -2+3.25 = 1.25





e=c-45





add 45 to both sides to get





e+45=c-45+45





e+45=c





so





c=e+45





180-y=x





subtract 180 from both sides





-y = x-180





now multiply both sides by (-1)





-y(-1)=(x-180)(-1)





y = -x+180





y=180-x
Reply:2/3 -(-4/5) any time you have minus a negitive number it is as if you take the negitive value and multiply it by negitive 1.


So


2/3 -(-4/5) becomes 2/3 + 4/5


Then you have to do the work to make the denominators the same and then you can just add them together and then simply your answer:





2/3 = 2/3 * 5/5 = 10/15


4/5 = 4/5 * 3/3 = 12/15





Remember any number over itself is equal to 1 and any number times 1 = itself so if you multiply the top and bottom numbers of a fraction by the same number its like multiplying it by 1.





so 2/3 + 4/5 = 10/15 +12/15





Now that the denominators are the same you can just add the numerators together and get 22/15.





Which simplified = 1 7/15





11-(-10) same thing becomes 11 + 10


again getting across the principal that any negitive number times a -1 equals a positive number.





Also when you see -(-10) that is mathimatical short hand for


-1 * (-10). And multiplying by -1 will always change the sign.





try the rest on your own.
Reply:2/3 - (-4/5)


Get the common denominator (15)





2/3 = 10/15 (2x5/3x5)





-4/5 = 12/15 (4x3/5x3)





10/15 - (-12/15)





Now a minus a minus (negative) number is adding - two negatives make a positive


example: -10 - 10 = -20 //// -10 -(-10) = -10+10 = 0





10/15 + 12/15 = 22/15 reduce 1 7/15


-------


Minus a minus


11+10 = 21


-------


x-y-z


Substitute the know values of x, y, %26amp;z





10.5 - 3.8 - 1.7(?) = 5


I'm not sure you wrote Z correctly


--------


a-(b-c)=


Substitute


-2 - (-3 - 1/4)


or


-8/4 - (-12/4 - 1/4) = (-8+12-1)/4 = or (12-8-1)/4 = 3/4


-------


E=C-45 add 45 to both sides


E+45 =C


-----


180-Y=X


-Y=X-180


Y = -X+180


or


180-Y=X add Y to both sides and subtract X from both sides


180-X = Y