Question

Colllect like terms 21b+b=  (simpify answer)

Answer 1

21 of anything plus one more of the same thing add up to 22 of those things. In this exercise, the 'things' happen to be 'b's.

Answer 2

To simplify this expression we collect like terms. The 'b' terms can be added together to get the final value:
$21\cdot b + b = 21\cdot b + 1 \b = 22 \b$