This is a system of equations problem. You can either solve it with elimination or substitution.
Let c = candy bar and b = bubble gum.
Elimination:
c + b = $1.50, and c - b = $1
Add the equations
c + b + c + (- b) = $1.50 + $1
2c = $2.50
c = $1.25
$1.25 + b = $1.50
b = $0.25
Substitution:
c + b = $1.50, and c - b = $1
c = $1.50 - b, so $1.50 - b - b = $1
$1.50 - 2b = $1
- 2b = - $0.50
b = $0.25
Since we don't actually have to solve for the candy bar, we can stop.
