Answer: 217.52 N
Explanation: The applied force is 20 N, the distance covered is 12.0 m and the angle is 25° above the horizontal.
Hence the formulae that defines work done is given by
W = Force × distance
But since the force has been inclined at an angle θ above the horizontal, the horizontal component of force is neccesary to produce the required motion to make the child do work on the wagon.
Hence
Work done = (horizontal component of force) × distance
Work done = F cos θ × distance
Work done = 20 cos 25 × 12 = 217.52 N
<h3>Question:</h3>
How to find g (acceleration due to gravity)
<h3>Solution:</h3>
We know,
Acceleration due to gravity (g)

where, G = Gravitational constant

M = Mass of the earth

R = Radius of the earth

Putting these values of G, M and R in the above formula, we get

So, the value of acceleration due to gravity is

Hope it helps.
Do comment if you have any query.
Answer:
It's a pretty simple suvat linear projectile motion question, using the following equation and plugging in your values it's a pretty trivial calculation.
V^2=U^2+2*a*x
V=0 (as it is at max height)
U=30ms^-1 (initial speed)
a=-g /-9.8ms^-2 (as it is moving against gravity)
x is the variable you want to calculate (height)
0=30^2+2*(-9.8)*x
x=-30^2/2*-9.8
x=45.92m