-- Remember how to find an average:
-- Add up all the items on the list.
-- Divide the sum by the number of items on the list.
-- John's first 3 test scores were 94, 98, and 98 .
-- His score on the 4th test will be 'F' .
-- His average after the fourth test will be
(94 + 98 + 98 + F) / 4 .
-- He wants that average to be 96.
96 = (94 + 98 + 98 + F) / 4
There's your equation.
