a/m - b = c for m

[math_celebrity]

a/m - b = c for m

Add b to both sides:
a/m - b + b = c + b

Cancel b on both sides:
a/m = c + b

Multiply each side by m:
am/m = m(c + b)

Cancel the m's on the left side:
a = m(c + b)

Divide each side by (c + b)
a/(c + b) = m(c + b)/(c + b)

Cancel the (c + b) on the right side, and we get:
m = a/(c + b)