Find the value of 4a + 3b when a=2 and b=5

This question is asking us to place a number in the place of their corresponding letter, so as the letter a is attached to the number two, whenever we see the letter a in the equation we would replace it with two, and the same applies for the letter b. So this equation would now read four times two plus three times five, and we would shorten this down by writing; four times two equals eight, and three times five equals fifteen, then eight plus fifteen equals twenty-three, which is your answer.