Question

Which is more work, pushing with 115 N over 15m or lifting 20N over 10 m?

Answer 1

Work is simply the force applied over a distance.

Work = Force × Displacement (m) ...In some cases where an angle is involved cosФ (theta) is used 
Work = F × D(m) × Cos(an angle measure)

So for lifting the object cos(90°) would be used...while pushing cos(0°)
When you work out the formula for each it should be clear what the correct answer is. 

Answer 2

Work = (force) x (distance)

You could look at the two cases, and see right away that
the first one has more force acting through more distance,
so it must be more work.  But since I just gave you the formula
for Work, let's calculate the amount of it for both cases:

First case:  Work = (115 N) x (15 m) =   1,725 joules

Second case:  Work = (20 N) x (10 m)  =  200 joules

The first case involves 8.625 times as much work as the second case.