Step 1) Expand the terms in parenthesis on the right side of the equation by multiplying each term within the equation by the term outside the equation:

#8.7 = 3.5m - (2.5 xx 5.4) + (2.5 xx 6m)#

#8.7 = 3.5m - 13.5 + 15m#

Step 2) Group and combine like terms on the right side of the equation:

#8.7 = 3.5m + 15m - 13.5#

#8.7 = (3.5 + 15)m - 13.5#

#8.7 = 18.5m - 13.5#

Step 3) Add #color(red)(13.5)# to each side of the equation to isolate the #m# term while keeping the equation balanced:

#8.7 + color(red)(13.5) = 18.5m - 13.5 + color(red)(13.5)#

#22.2 = 18.5m - 0#

#22.2 = 18.5m#

Step 4) Divide each side of the equation by #color(red)(18.5)# to solve for #m# while keeping the equation balanced:

#22.2/color(red)(18.5) = (18.5m)/color(red)(18.5)#

#1.2 = (color(red)(cancel(color(black)(18.5)))m)/cancel(color(red)(18.5))#

#1.2 = m#

#m = 1.2#