Two forces FA and FB are applied to an object whose mass is 13.0 kg. The larger force is FA.?

[811]

Help me plz!
(kindly state the steps)

Two forces FA and FB are applied to an object whose mass is 13.0 kg. The larger force is FA. When both forces point due east, the object's acceleration has a magnitude of 1.27 m/s2. However, when FA points due east and FB points due west, the acceleration is 0.837 m/s2, due east. Find (a) the magnitude of FA and (b) the magnitude of FB

[Jim]

The combined SIZE of the two forces (FA + FB) = m(a1) = (13.0)(1.27) = 16.51 N
The SIZE difference (FA - FB) of the two forces = m(a2) = (13.0)(0.837) = 10.881 N

FA + FB = 16.51
FA = 16.51 - FB

FA - FB = 10.881
16.51 - FB - FB = 10.881
-2FB = -16.51 + 10.881 = -5.629
FB = 5.629/2 = 2.8145 ≈ 2.81 N ANS(b)
FA = FB + 10.881 = 2.8145 + 10.881 = 13.6955 ≈ 13.7 N ANS (a)