Nadine bought two shirts and three pairs of pants at a back-to-school sale. the shirts cost $16.50 each and the pants cost $19.95 each, tax included. if she paid with a $100 bill, how much change should she receive?

First you would make an equation.
S= shirts; P= pants 
 2(s) +3(p)= 100
you would inout how much each item costed. 2(16.50) +3(19.95)=100
2(16.50)= $33 and 3(19.95)= $59.85
you would add your answers together $33+$59.85= $92.85
to find out the amount of change left over from a $100 you would subtract the total cost from 100. 
$100-$92.85= $7.15
your final answer would be $7.15