t = state income return (without sales tax)
106% of t = 4960.80
AKA
1.06t = 4960.80 --> Divide both sides by 1.06 to find the state income return without sales tax
t = 4680
Subtract t from the state income return with sales tax.
4960.80 - 4680 = 160.80
She paid $160.80 in sales tax.
