Two maths question, need invaluable help

hihi,

Question 1 : Paul had 30 more marbles than Peter. After Peter gave Paul 15 marbles, Paul has twice as many marbles as Peter.

How many marbles did they have altogether?

How many marbles did each of them have?

Question 2 : A spherical balloon is being deflated in such a way that the volume is decreasing at a constant rate of 120 cm3 s-1. At time t s, the radius of the balloon is r cm.

Find the rate of change of the radius when r =30

Find the rate of change of the surface area when the volume is 36 π4 cm3

Thank you all (Clapping)