Question 851524
Here's what we know:
A = J + 20 (Amanda is 20 years older than Jenny)
A + J = 44 (the sum of their ages is 44.)
Substitute the value of A into the second equation.
(J+20) + J = 44
Add
2J + 20 = 44
Subtract 20 from each side
2J = 24
Divide each side by 2
J = 12
.
If Jenny is 12, then Amanda is 12+20, or 32.
Do those add up to 44?  Yes, 12+32 is 44.
Success!