martin bought 10 concert tickets , some at the full price of $ 2.00 per ticket , and some at a discounted price of $ 1.60 per ticket . if he spent a total of $ 18.00 , how many discounted tickets did he buy ?
"let x be the number of tickets he bought at $ 2 per ticket . then 2 x + ( 10 - x ) 1.6 = 18 0.4 x = 2 = > x = 5 discounted tickets = 10 - x = 5 ans : c"
subtract(multiply(10, 2.00), multiply(1.60, 10))