n There are 300 pupils in a stadium. 40% of them were boys. 60 more boys entered the stadium. What percentage of the pupils in the stadium are boys now?   1. 20% 2. 30% 3. 50% 4. 60%AnswerSimply set up a systems of equations. let x=NUMBER of boys, and let y=number of girls. since there are 30 more boys than girls, we can say that y+30=x, or the amount of boys is equal to the number of girls plus thirty more. We can also say that the total number of students in the CLASS is 130, so x+y=130, or the number of girls plus the number of boys is equal to 130 students. x+y=130 y+30=x Because x is y+30, we can substitute the x in the first equation with y+30, so x+y=130 is (y+30)+y=130 is y+y+30=130 is 2y+30=130 Subtract thirty from both sides, and you get 2y=100 Divide by two, and get y, or the number of girls, is equal to 50 students. Looking BACK to the first equation, substitute 50 for y, and get; x+y=130 is x+50=130 subtract 50 from both sides, you get x, or number of boys, is 80 students.