In a group of students , 12 read maths, 15 read statistics , 11 read physics, 4 read maths only , 7 read statistics only, 3 read statistics and physics only and 1 read maths and statistics only . What is the number of the students who were there altogether ( universal set)

23 students

Step-by-step explanation:

In a group of students , 12 read maths, 15 read statistics , 11 read physics, 4 read maths only , 7 read statistics only, 3 read statistics and physics only and 1 read maths and statistics only.

Those that read maths only = 4, Those that read statistic only =7, Those that read statistics and physics only = 3, those that read maths and statistics only = 1.

Therefore those that read all three subjects = 15 - 7 - 3 - 1 = 4

Those that read maths and physics only = 12 - 4 - 4 - 1 = 3

Those that read physics only = 11 - 3 - 4 - 3 = 1

The number students = 4 + 7 + 3 + 1 + 4 + 3 + 1 = 23 students

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18

8+10

step-by-step explanation:

you multiply 4 by 2 and 5 by 2