Given:
M=10KG
F=42N
Opposing Force=6N
If we can recall F=ma, we can easily calculate the acceleration by substituting the given variables; but in our case, we have an opposing force. So we have to subtract the opposing force from the horizontal force.
F = ma
42N-8N=10KG x a
34N = 5KG x a; divide both sides by 10KG for a to be sole variable
34kg m/s^2) / 10kg x a (Newtons are sometimes referred to as kg m/s^2)
3.4 m/s^2 = a ; (kg's are cancelled)
Therefor, our acceleration is 3.4 m/s^2.