Hello!
To solve whatever z is we have to get it by itself by using inverse operations. I will undo operations below.
m=q/z-v+v
m+v=q/z(z)
m+v+z=q
m+v+z-z=q-z
m+v=q-z
Here I will switch z to adding negative z so we can use the commutative property.
m+v= q+(-z)
m+v=-z +q
m+v-q=-z+q-q
m+v-q=z
We now have our formula for z. z=m+v-q. Hope this helps!