t + f = 12
25t + 65f = 420
Solve for t
t = 12 - f
25(12 - f) + 65f = 420
300 - 25f + 65f = 420
40f = 420 - 300
40f = 120
f = 120/40
f = 3
Find t
t = 12 - 3
t = 9
So, f = 3 and t = 9
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