If we know that she got 75%, we can write it as the fraction 75/100.
We also know that she got 60 correct out of an unknown number of questions, which we can call 'x'
We means we know that 75/100 = 60/x (the number of questions)
Cross multiply to get an equation.
75 * x=60 * 100 -----> 75x=6000
Divide both sides by 75 to solve for x.
6000/75=80
x=80, meaning that her test had 80 questions on it.