Solve. URGENT PLS

b=3/4a

a+b=21

what is a what is b?!

One card is dealt from a 52 card deck. find the probability that the dealt card is a 4 or a black 7

Linda loans her friend $250 with a 5% monthly intrest rate. how much was the whole loan?

This is a rational expression because the denominator contains a variable. this is a polynomial with 3 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 4 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 4 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 3 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 5 terms.