When ringing up a customer, a cashier needs 30 seconds to process payment as well as 3 seconds to scan each item being purchased. How long does it take to ring up a customer with 24 items? Write and solve an equation to find the answer.

Say x = the number of items being purchased. Then we can write the equation, using seconds:

3x + 16 = 136

(3 seconds per item, plus 16 seconds to process payment, equals 136 seconds total.)

Subtract 16 from each side. Then divide both sides by 3.