Hi!
Let's start with the facts:
Therefore:
[tex]\frac{m}{4}=43[/tex]
Now, we have an algebraic equation. In order to solve, we must multiply both sides by 4 so that way m is by itself.
[tex]\frac{m}{4}*4=43*4[/tex]
[tex]m=172[/tex]
Therefore, Mandy received 172 messages. (that's a lot of messages!)
For another example of solving an equation algebraically, see:
https://brainly.com/question/17595716
https://brainly.com/question/2534559