Marcus tried to solve an equation.
\begin{aligned} 2.5b&=5\\\\ \dfrac{2.5b}{2.5}&=\dfrac{5}{2.5}&\tealE{\text{Setting up}}\\\\ b&=3&\purpleD{\text{Calculating}} \end{aligned}
2.5b
2.5
2.5b
b
=5
=
2.5
5
=3
Setting up
Calculating
Where did Marcus make his first mistake?
