Question 967176
A=injuries in amusement parks; B=injuries in boat building=A-12: I=injuries in iron foundries=A+30
A+B+I=387 Substitute for B and I
A+(A-12)+(A+30)=387
3A+18=387 Subtract 18 from each side.
3A=369 Divide each side by 3.
A=123 ANSWER 1: There were 123 injuries in Amusement Parks and Arcades.
B=A-12=123-12=111 ANSWER 2: There were 111 injuries in Boat Building.
I=A+30=123+30=153 ANSWER 3: There were 153 injuries in Iron Foundries.