Make t the subject of the formula

p = 50 + 30t

Make t the subject:
p = 30 t+50

p = 30 t+50 is equivalent to 30 t+50 = p:
30 t+50 = p

Subtract 50 from both sides:
30 t = p-50

Divide both sides by 30:
Answer: | t = p/30 - 5/3