Equations 6-7:
F-T=m1a Box 1
T=m2a Box 2

Eliminated tension T by adding the two equations then solved for the acceleration to give
Equation 6-8:
a= F/(m1+m2)

Substituted this expression into Box 2 equation to find T.

Equation 6-9:
T=(m2/m1+m2)F Using the equation for box 2.
It is left as an exercise to show that the equation for box 1 gives the same expression for T. Please show me step-by-step how to make the equation for box 1 give the same expression for T.