To solve this question you need to make an equation including each variable: the extra $10, the $8 per hour (we'll represent hours as h) and the total amount of money, $66. Then simply solve the equation to get your final answer.
10 + 8h = 66
8h = 56 Subtract 10 from both sides
h = 7 Divide both sides by 8
In other words, he worked 7 hours.