The first thing to do is isolate the #m# term on one side of the equation and the constants on the other side of the equation while keeping the equation balanced:
#4/5m + 2 - color(red)(2) = 6 - color(red)(2)#
#4/5m + 0 = 4#
#4/5m = 4#
Now, solve for #m# while keeping the equation balanced:
#color(red)(5/4) * 4/5m = color(red)(5/4) * 4#
#color(red)(cancel(color(black)(5)))/color(blue)(cancel(color(black)(4))) * color(blue)(cancel(color(black)(4)))/color(red)(cancel(color(black)(5)))m = 5/color(green)(cancel(color(black)(4))) * color(green)(cancel(color(black)(4)))#
#m = 5#