Question

a. Write an expression that represents the following expression using the variable b: "Billy's age in 8 years." b. Write an equation using the expression above if in 8 years Billy will be 21 years old. c. How old is Billy now? d. Write and solve a word problem that matches the equation: a - 6 = 10.

Answer 1

a. b+8
b. b+8=21
c. b=21-8=13 Billy is 13 now
d. Ann was ten years old six years ago. How old is she now? a-6=10, a=16. Ann is 16 now.

Answer 2

"Billy's age in 8 years", this refers to a future age, which implies adding 8 years to the present age. The expression would be:

`B+8`

"In 8 years Billy will be 21 years", this expression, using the first one too, would be:

`B+8=21`

How old is Billy now?

The answer to this question is the solution of the second equation:

`B+8=21\\B=21-8=13`

Billy is 13 years old now.

A problem for the expression
`A-6=10` could be:

Six years ago Adam was 10 years old.

The six years in the past refers subtracting, and the age back then is the result of that difference.