b = number of boxes of crayons Ms Cohen buys
Let:
M = amount of money you she spend
She wants to buy boxes of crayons that cost $2 per box. She also buys a poster for $5. Ms. So:
![2b+5](https://img.qammunity.org/2023/formulas/mathematics/college/ltorbwvdmo97ps34fpk0gkg6kmk2gy20pz.png)
Since she can spend at most $30:
![2b+5\le30](https://img.qammunity.org/2023/formulas/mathematics/college/4vl1j9rwlrc542ehfvm1yurigvyyvejzwd.png)
![\begin{gathered} \text{Solve for b:} \\ \text{subtract 5 from both sides:} \\ 2b+5-5\le30-5 \\ 2b\le25 \\ \text{divide both sides by 5} \\ (2b)/(2)\le(25)/(2) \\ b\le12.5 \\ \text{ to the nearest whole:} \\ b\le12 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/yyg9e3bl9y5xoke1b02oh7gu9tulv2n29u.png)
she can buy at most 12 boxes of crayons