Mary Lou has 2 more nickels than pennies, and she has 30 coins all together. Use x for the number of pennies.
A2(x + 2) = 30
Bx + (x + 2) = 30
C2x + 30 = 5
Dx + 2 = 30
A2(x + 2) = 30
Bx + (x + 2) = 30
C2x + 30 = 5
Dx + 2 = 30