First, eliminate the parenthesis by multiplying each term within the parenthesis by the term outside the parenthesis:
#color(red)(2.4)(m - 3) + 3.8 = -8.7#
#(color(red)(2.4) xx m) - (color(red)(2.4) xx 3) + 3.8 = -8.7#
#2.4m - 7.2 + 3.8 = -8.7#
#2.4m - 3.4 = -8.7#
Next, add #color(red)(3.4)# to each side of the equation to isolate the #m# term while keeping the equation balanced:
#2.4m - 3.4 + color(red)(3.4) = -8.7 + color(red)(3.4)#
#2.4m - 0 = -5.3#
#2.4m = -5.3#
Now, divide each side of the equation by #color(red)(2.4)# to solve for #m# while keeping the equation balanced:
#(2.4m)/color(red)(2.4) = -5.3/color(red)(2.4)#
#(color(red)(cancel(color(black)(2.4)))m)/cancel(color(red)(2.4)) = -2.208bar3#
#m = -2.208bar3#
