(b)+(b+45)=215 b = # of boys there are 45 more girls than boys and 215 students total. minus 45 on both sides leaving you with (b)+(b)=170 combine like terms leaving you with 2b=170 divide both sides by 2 b=85 there were 85 boys 85+45=130 (the 45 for the # of girls more than boys) there were 130 girls.
