[tex]m\text{ }=\text{ }\frac{12p\text{ - 60}}{45}[/tex]Explanation:
Average monthly price:
[tex]p\text{ = }\frac{45m+60}{12}[/tex]
We make m the subject of formula:
First we cross multiply
[tex]\begin{gathered} p\text{ (12)= }45m+60 \\ 12p\text{ =}45m+60 \\ \text{subtract 60 from both sides:} \\ 12p\text{ - 60 = 45m + 60 - 60} \end{gathered}[/tex][tex]\begin{gathered} 12p\text{ - 60 = 45m + 0} \\ 12p\text{ - 60 = 45m} \\ \text{divide both sides by 45:} \\ \frac{12p-60}{45}=\text{ }\frac{45m}{45} \end{gathered}[/tex][tex]m\text{ }=\text{ }\frac{12p\text{ - 60}}{45}[/tex]
First box = 12p
Second box = 60
Third box = 45