Scooby made 70 percent on his science test. if he got 21 problems correct how many problems are on the test

Since the score is 21 out of an unknown number, and the percantage is 70%, you set. 7 equal to the score (21/x), and solve for x

.7 = 21/x

Multiply both sides by x

.7x = 21

Divide both sides by. 7

x = 30