Question

Shannon sells handmade wallets for $12 each.

Answer 1

She sold n yesterday
today she sold n-3

ok, so
12(n+n-3)=396
12(2n-3)=396
divide both sides by 12
2n-3=33
add 3 to both sides
2n=36
divide both sides by 2
n=18

sold 18 wallets yesterday