2x + y = 10 x - 2y = -5
if (x, y) is the solution to the system of equations above, what is the value of 3x - y?

3x - y = 5

2x + y = 10  | ×2

x - 2y = -5

4x + 2y = 20

x - 2y = -5

add

4x + x + 2y - 2y = 20 - 5

5x = 15

x = 15 : 5

x = 3

replace x

4(3) + 2y = 20

12 + 2y = 20

2y = 8

y = 8 : 2

y = 4

3x - y =

= 3(3) - 4

= 9 - 4

= 5

percentage - 25%

probability - 0.25

we know,

total amount of students in class = 20

total boys = 10

total girls = 10

no of girls who wear glasses = 10/2 = 5

probability of choosing a girl with glasses is =

number of girls wearing glasses/total number of students in the class = 5/20

thus, percentage of selecting a girl wearing glasses will be

= 5/20 × 100

= 5 × 5

25%

therefore,

probability will be 0.25

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