Question 791474
This is a mixture problem.  


First, assign variables to everything:
H = 60% fat
T = 12.5% fat
L = 10% fat
M = 200 kilograms
u = unknown amount of the 10% fat candy
v = unknown amount of the 60% fat candy


Form the equations to describe the system:
{{{(Lu+Hv)/M=T}}} and {{{u+v=M}}}


Solve the system for u and v.
{{{v=M-u}}}.
Substitute.
{{{Lu+H(M-u)=MT}}}
{{{Lu+HM-Hu=MT}}}
{{{Lu-Hu+HM=MT}}}
{{{(L-H)u+HM=MT}}}
{{{(L-H)u=MT-MH}}}
{{{u=(MT-MH)/(L-H)}}}
{{{highlight(u=M(T-H)/(L-H))}}}  --------just watch the signs carefully.
And conclude for the other quantity, {{{highlight(v=M-M(T-H)/(L-H))}}}


Now just substitute given values to find values of u and v.