A school ordered 3 large boxes of board markers. After giving 15 markers to each of 3 teachers, there were 90 markers left. The diagram represents the situation. How many markers were originally in each box?

Answer: 45 markers in each box.

Step-by-step explanation:

Initially, the school had 3 boxes of board markers, and each box had X board markers, where X is the number we want to find.

Then the initial number of board markers is 3*X.

We know that after giving 15 markers to 3 teachers, we have other 90 markers left. This can be written as:

total markers = markers for the teachers + markers left

3*X = 15*3 + 90 = 45 + 90 = 135

now, we divide both sides by 3.

X = 135/3 = 45

From this, we know that in each box we have 45 markers

15 x 3 = 75 markers given to teachers

75 + 90 = 165 markers in total

165 : 3 = 55 markers per box (answer)