Redlands School sent x students to a revision day.

St Samuel's School sent twice as many students as Redlands School.

Francis Long School sent 7 fewer students than Redlands School.

Each student paid £15 for the revision day

The students paid a total of £1155

Work out how many students were sent by each school to the revision day

Show all working out.

Let x be the number of students that Redlands School sent to a revision day.

If St Samuel's School sent twice as many students as Redlands School, then St Samuel's School sent 2x students.

If Francis Long School sent 7 fewer students than Redlands School, then Francis Long School sent x-7 students.

The total number of students is

x+2x+x-7=4x-7.

Each student paid £15 for the revision day, then all together they paid £15· (4x-7) that is £1155. Solve this equation:

15· (4x-7) = 1155,

60x-105=1155,

60x=1155+105,

60x=1260,

x=1260:60,

x=21.

Then,

Redlands School sent to a revision day 21 students; St Samuel's School sent to a revision day 42 students; Francis Long School sent to a revision day 14 students.