Can someone explain these physics problems

These are a few questions that I am reviewing for a test, and I'm pretty lost. If someone can explain these in detail, that would be greatly appreciated. Thanks!!

A mass of 25 kg is acted on by two forces: F1 is 15 N due east, and F2 is 10 N due north. Find the magnitude and direction of its acceleration.

A force F produces an acceleration a on an object of mass m. A force 3F is exerted on a second object, and an acceleration 8a results. What is the mass of the second object?

A gust of wind blows an apple from a tree. As the apple falls, the force of gravity on the apple is 9.25N downward and the force of wind on the apple is 1.05 N to the right. Find the magnitude and direction of the net external force on the apple.

1) acceleration a = Fr / M = square root of ( 225+100) / 25 = 0.72 m/sec^2 in a direction tan^-1(2/3) North of East.
2) mass m = force / acceleration = 3 F / 8 a = (3/8) F/a = 3 m / 8

3) net force F = square root of ( 9.25^2 + 1.05^2) = 9.309 N at tan^-1( 0.1135) with the vertical.

prob 1 .
first square f1 and f2 ,then add them, then find their square root. this is force .then find a=f/m
ans a=1.387 m/s2
prob 2
m= 8/3 m.from newtons sec law.
prob 3
square and add forces , then find root.
hope that helps.