we write system of equations:
O = 5a
P = 15a
a,b,c =?
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a + b + c = 5a b + c = 4a
ab/2 = 15a b/2 = 15
Now we calculate b and remaining sides:
b = 30
30 + c = 4a
c^2= 30^2 + a^2
(4a - 30)^2 = 900 + a^2
16a^2 - 240a + 900 = 900 + a^2
15a^2 = 240a
a = 16
that means that c = 416-30 = 34