Every week, Ailing saves $2m, Bala saves$(m + 5) and Carrie saves $(3m - 2).

1. Find the total weekly savings of the three children

$\text{Total savings} = 2m + (m + 5) + (3m - 2)$
$= 6m + 3$

2. Calculate the average weekly savings

$\text{Average savings} = \frac{6m + 3}{3}$
$= 2m + 1$

1. Substitute $m = 4$ into the expression for average savings

From part (a), the average savings is $\frac{2m + (m + 5) + (3m - 2)}{3} = \frac{6m + 3}{3} = 2m + 1$.
When $m = 4$,
$\text{Average savings} = 2(4) + 1 = 8 + 1 = 9$