In the first case, the force acting on the spring is the weight of the mass:

This force causes a stretching of

on the spring, so we can use these data to find the spring constant:

In the second case, the first mass is replaced with a second mass, whose weight is

And since we know the spring constant, we can calculate the new elongation of the spring:
3 times 6= 18. The average speed is 19 mph.
hope this helps!
The first rubber balloon was made by Professor Michael Faraday in 1824, out of two sheets of rubber whose edges were pressed together. Hot air balloonwas the balloon to make the first recorded manned flight. It was made by the Montgolfier brothers and launched on 21 November 1783.
150*4=600
So the answer is 600