We want to determine x from the expression
b(5px - 3c) = a(qx - 4)
Expand each side.
5bpx - 3bc = aqx - 4a
Subtract aqx from each side.
5bpx - aqx - 3bc = - 4a
x(5bp - aq) - 3bc = - 4a
Add 3bc to each side.
x(5bp - aq) = 3bc - 4a
Divide each side by 5bp - aq
x = (3bc - 4a)/(5bp - aq)
Answer: [tex]x= \frac{3bc-4a}{5bp-aq} [/tex]