If PQ=3x+4 and the perimeter of PQR=57, find the value of x

What are “like terms”? why can we only add like terms?

Ten members of balin's soccer team ran warm ups for practice. each member ran the same distance. their combined distance was 5/6 of a mile. to find the distance that each member ran, balin wrote the expression below.

Yvaries inversely as x. y =12 when x=5. find y when x=4