Statistics: Averages and Arithmetic Means Classwork

1. D

$\eqalign{\dfrac{220+x}{4}&=80\\220+x&=320\\x&=100}$

2. B

$\eqalign{\dfrac{7+22+x}{3}&=25\\29+x&=320\\x&=100}$

3. E

$\eqalign{\dfrac{x}{4}&=68\\x&=272\\\dfrac{272+y}{5}=70\\y=78}$

4. 97

$\eqalign{\dfrac{x}{7}&=88\\x&=616\\\dfrac{616+2y}{9}=90\\y=97}$