John buys 3 dress shirts.  They sell for $20 each.  He also has to pay 10% tax on everything.  How much did he pay in total?
The shirts cost 3*$20=$<T>multiply(3, 20)=60 before tax
The tax cost $60*.1=$<T>multiply(60, 0.1)=6.0
So in total they paid $60+$6=$<T>add(60, 6)=66
