Let #m# be Mac's Mass
and convert the description a bit at a time into algebraic form:
5kg more than 3 times #color(green)("Mac's Mass")# is decreased by twice #color(green)("his mass")#, the result is 60kg
#rArr#5kg more than 3 times #color(green)(m)# is decreased by twice #color(green)(m)#, the result is 60kg
5kg more than #color(red)(3" times "m)# is decreased by #color(blue)(" twice "m)#, the result is 60kg
#rArr#5kg more than #color(red)(3m)# is decreased by #color(blue)(2m)#, the result is 60kg
#color(green)(5"kg more than "3m)# is decreased by #2m#, the result is 60kg
#rArr##color(green)(5+3m)# is decreased by #2m#, the result is 60kg
#color(red)((5+3m)" is decreased by "2m)#, the result is 60kg
#rArr#
#color(red)((5+3m)-2m)#, the result is 60kg
#((5+3m)-2m)##color(blue)(" the result is "60"kg")#
#rArr##((5+3m)-2m)##color(blue)(=60"kg")#
So we have:
#(5+3m)-2m = 60#
Combining the #m# terms on the left side:
#5+m = 60#
Subtracting #5# from both sides:
#m = 55#
