#### Answer

(a) The family saves $\$290$ each month.
(b) $\$3480/year$

#### Work Step by Step

(a)
We are told that the family spends $90\%$ of its earnings, which means it saves $100\%-90\%=10\%$. Since the total earnings are $\$2900$, we can find out the amount saved with a proportion:
$\frac{x}{2900}=\frac{10}{100}=\frac{1}{10}$
We cross-multiply:
$x*10=2900*1$
$x=2900/10=290$
Thus the family saves $\$290$ each month.
(b)
To find out the annual savings, we multiply the monthly savings by the number of months in a year (12):
$290*12=\$3480/year$