Math problems need help ASAP by tonight?

Need help wit a few math problems jst plz help me and explain plz how i do so.





1.) 5t/4a + b/3a -3b/a





(a) 3b/8a (b) 17b/12a (c) -17ab/12a^ (d) -17b/12a (e) none of these





2.) the population of snowtown was 4500 in 1990 it had decreased to 3600.Find the % decrease in population during those four years.





(a) 80% (b)90% (c)16.2% (d) 20% (e) none of these





plz tell me wat u did to firgure this out plz nthnx








3.) simplify 2 -1/4 divide 3 -1/5





(a) 7/5 (b) 5/8 (c) 8/5 (d)45/64 (e) none of these





And


1 Divide 1/a +1/a =





(a) a+b/ab (b) ab /a+b (c) a^ +b^ (d) a^-b^ (e) none of these





ONCE AGAIN THN U SOO MUCH, i really dont like math n if u can explain how u got the answer that would very much help

Math problems need help ASAP by tonight?
1)


5t/4a + b/3a -3b/a





u need to get the least common multiplier between these denominators


4a ,3a ,a ----%26gt;LCM =12 a


so divide 12a by every denominator then multiply the reault by the numerator


i.e.


for the term 5t/4a


12a/4a =3 so mutiply 3 by 5t =15 t


so 5t/4a =15t/12a





b/3a = 4b/12a


3b/a = 36b /12a


so the result is 15t/12a + 4b/12a - 36b/12a = (15t+4b - 36b)/12a = (15t - 32b)/12a





if the 1st term is 5t/a so the the answer is none of the these


but if it is 5b/a so the result will be -17b/12a


(check the question again )


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2)


the answer will be 100 *(4500 -3600) /4500 %= 100 * 900 /4500 %= 20 %


so the answer is (d) 20 %


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3)


(2-1/4)/(3-1/5) mutilpy above %26amp; below by 20


=(40 -5)/(60-4) =35 /56 =5 / 8


so the answer is (b) 5/ 8


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4)


(I think u typed it wrong )


1/( (1/a) +1/b) (mutiply above %26amp; below by ab


=ab /(b+a)


so the answer is (b) ab/(a+b)