When we resolve the force 10N making an angle 60o with the horizontal we get
F'=10 cos60=10×(√3)/2=5(√3)N ,this force is acting along X axis
We have another force F acting along Xaxis that is 5N but it is in opposite direction so
the resultant force will be
R=F'-F=5(√3)-5 (because F <F')
Since the above resultant R is not zero therefore acceleration is along X axis
Extra Info
The acceleration along X axis can be taken as +ve or -ve because if we take the
direction of force 5N as +ve X axis direction the the acceleration is in -'ve direction.
But if we take direction of force 5(√3)N as +ve X axis direction then acceleration is +ve.
Now to find acceleration
Ftotal=R
Ma=5(√3)-5
a=5 [ (√3)-1]/√3 (given M=(√3) kg)
After calculation of acceleration it is approximately
a=2.11 m/s2