Answer:
15
Step-by-step explanation:
Gregory gained 86 dollars in total and he got this money by first getting 11$ and then 5$ for each question he solved correctly, so our equation is
11+5x=86 (x being the number of questions he answered correctly)
11+5x=86 (subtract 11 from both sides)
5x=75 (divide both sides by 5)
x=15
Gregory answered 15 questions correctly
