what is the total cost of 2 sandwiches at $ 2.45 each and 4 sodas at $ 0.87 each ?
"answer = a 2 * 2.45 + 4 * 0.87 = 2 ( 2.50 - 0.05 ) + 4 ( 1.00 - 0.13 ) = 5 + 4 - 0.1 - 0.52 = 9 - 0.62 = 8.38"
add(multiply(2, 2.45), multiply(4, 0.87))