#=> 1/2(m - 6) = 3 + m/5#
#=> (m - 6)/2 = 3 + m/5#
#=> m/2 - 6/2 = 3 + m/5#
#=> m/2 - 3 = 3 + m/5#
#=> m/2 - m/5 = 3 + 3#
#=> m[1/2 - 1/5] = 6#
#=> m[(1/2 × 5/5) - (1/5 × 2/2)] = 6#
#=> m[5/10 - 2/10] = 6#
#=> m[(5 - 2)/10] = 6#
#=> m(3/10) = 6#
#=> m = 6 × 10/(3) = cancel(3) × 2 × 10/cancel(3)#
#=> m = 20#