Question

the average of three number is 10 if the average of two number is 11 find the third number answer with solution ​

Answer 1

the average of three number is 10

$\frac{x + y + z}{3} = 10 \\ x + y + z = 30$

the average of two number is 11

$\frac{x + y}{2} = 11 \\ x + y = 22$

Substrate equation 1 and 2 -

we get,

$z = 30 - 22 = 8$