$\displaystyle (25*9.8)*0.2= 49 N$

$\displaystyle (8*9.8)*0.2=15.7 N$

So for the 25 kg mass the friction force is 49 N. The friction force for the 8 kg mass is 15.7 N

$\displaystyle F=ma

$

$\displaystyle Fa-Ff=ma$

$\displaystyle Fa=85$

$\displaystyle Ff=49+15.7=64.7$

$\displaystyle m=25+8=33

$

$\displaystyle 85-64.7=20.3

$

$\displaystyle 20.3=33a

$

$\displaystyle \frac{20.3}{33}=a=0.615

$

So the acceleration is 0.615 m/s^2

The answer is supposed to be 64.4N however I do not know how to get this answer. Help!