make m the subject of the formula p=m/2+2

Ok, that's how you do it:

p = \frac{m}{2} + 2

Subtract 2 from both sides:

p -2 = \frac{m}{2} \cancel{+ 2 -2}

p -2 = \frac{m}{2}

Multiply both sides by 2:

(p -2) \times 2 = \frac{m}{\cancel{2}} \times\cancel{ 2}

2(p -2)2 = m

m= 2(p -2)

m= 2p -4