You break even if you spend exactly as much as you gain. In other words, if the cost and the revenue are the same:
[tex]C(x)=R(x) \iff 145+0.25x=1.5x[/tex]
Subtract 0.25 from both sides:
[tex]145=1.25x[/tex]
Divide both sides by 1.25:
[tex]x=\dfrac{145}{1.25}=116[/tex]
So, they must sell 116 computers to break even. If they sell less, they'll lose money. If they sell more, they'll start making profit.
