Find the missing terms and write them in decreasing order of exponents. 21m7 − 7m5 + 49m = 7m( + + )

(I'm assuming the numbers after the variable "m" are the exponents)

21 - 7 + 49m = 7m(3 - + 7)

Whenever you see a term before a set of parentheses, it is indicating that when that term is divided from each term in the expression it is equal to, the quotient is whatever is in the parentheses. When you multiply every term in the expression in the parentheses by the term outside the parentheses, the product would equal the expression on the left. 

Hopes this helps!

*Btw, decreasing order of exponents means what it says. It's basically asking you to list your terms from greatest exponent to lowest exponent.

The answer would be the second choice : )