You break even if you spend exactly as much as you gain. In other words, if the cost and the revenue are the same:
![C(x)=R(x) \iff 145+0.25x=1.5x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/8otz9d0yki8atdavsfnql1m04ld6q7a5ai.png)
Subtract 0.25 from both sides:
![145=1.25x](https://img.qammunity.org/2020/formulas/mathematics/middle-school/jkjq0xz2mcjkcr71mtdedupli52ge81spg.png)
Divide both sides by 1.25:
![x=(145)/(1.25)=116](https://img.qammunity.org/2020/formulas/mathematics/middle-school/strvjbfensi8vndwavpk4ra8tqrhzipins.png)
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.