Question 1006226
y = k/x^2


y is the gravitaional force.
x is the distance between them.


y = 18
x = 10


y = k/x^2 becomes 18 = k/10^2 which becomes 18 = k/100.


solve for k to get k = 1800


now that you know k, you can solve the problem.


when the distance between them is 7.5 km, the equation becomes:


y = 1800/(7.5)^2 which becomes y = 1800/56.25 


solve for y to get y = 32.