A window cleaner has enough supplies to clean 21 windows per office building on a certain number of buildings. They can also clean the windows of a school with 42 windows. Altogether, there are enough supplies to clean 126 windows. How many office buildings can be washed? Identify the equation that would be used to solve this problem algebraically. (1 point)
O 42x + 21 = 126
O 21x - 42 = 126
O 42x - 21 = 126
21x + 42 = 126
The correct equation that would be used to solve this problem algebraically is:
21x + 42 = 126