This is similar to the previous problem, except we now have 2 unknowns.
Let x be the quantity of silver at 28% and y the quantity at 61%
Then x*28% + y*61% = 10*36%
and x + y = 10
write x (or y) in terms of the other variable using the second equation, then substitute back into the 1st equation and solve.
Morris: for some reason it's not wanting me to save a comment to your comment so I'll ad the additional work here.
Let y = 10-x then
28*x + (10-x)*61 = 360
28*x + 610 - 61*x = 360
collecting like terms:
33*x = 250 and x = 250/33 = 7.58 lbs.
so y = 10 - x = 2.42 lbs.
check: 7.58*28 + 2.42*61 = 359.8, so our work is correct.