The equation that can be as a result of the first step of applying substitution is as follows:
3a + (a - 15) = 225
Substitution is defined as putting in place of another. This is a technique used in solving algebraic equations. Therefore,
3a + b = 225
b = a - 15
Let's substitute the value of b in equation(i)
b = a - 15
Therefore,
3a + (a - 15) = 225
3a + a - 15 = 225
4a = 225 + 15
4a = 240
a = 240 / 4
a = 60
learn more on substitution here: https://brainly.com/question/524261
