A class has 30 boys and 20 girls. The average age of boys is 11 yrs and girls 12 What is the
average age of the whole class."

x = total age of boys

x / 30 = 11yrs

Multiply both sides by 30

x = 330

y = total age of girls

y / 20 = 12

Multiply both sides by 20

y = 240

(240 + 330) / 50 = 11.4 yrs

The average age of the whole class = 11.4 years.

step-by-step explanation:

y = | -2(-2) |     →     y = | 4 |     →     y = 4       ⇒   (-2, 4)

y = | -2(-1) |     →     y = | 2 |     →       y =   2       ⇒   (-1, 2)    

y = | -2(0) |     →     y = | 0 |     →       y = 0         ⇒   (0, 0)

y = | -2(1) |   c →     y = | -2 |     →     y =   2         ⇒   (1, 2)    

y = | -2(2) |     →     y = | - 4 |     →     y =   4         ⇒   (2, 4)