Draw a circle and divide into ten parts, red and 3 parts blue. a) What fraction of the circle is red? b) What fraction of the circle is blue?

Total people = $1 \text{ (you)} + 6 \text{ (friends)} = 7$ people.

Assuming the pizza is cut into 7 equal slices, each person will get 1 slice.
Each person will get $\boxed{\text{1 slice}}$.

Total people = $1 \text{ (you)} + 9 \text{ (friends)} = 10$ people.

Assuming the cake is cut into 10 equal slices, each person will get 1 slice.
Each person will get $\boxed{\text{1 slice}}$.

Total parts = 10.
Blue parts = 3.
Red parts = Total parts - Blue parts = $10 - 3 = 7$ parts.

Fraction red = $\frac{\text{Number of red parts}}{\text{Total parts}} = \boxed{\frac{7}{10}}$.

Blue parts = 3.

Fraction blue = $\frac{\text{Number of blue parts}}{\text{Total parts}} = \boxed{\frac{3}{10}}$.

Coloured parts = Red parts + Blue parts = $7 + 3 = 10$ parts.

Not coloured parts = Total parts - Coloured parts = $10 - 10 = 0$ parts.

Fraction not coloured = $\frac{\text{Number of not coloured parts}}{\text{Total parts}} = \frac{0}{10} = \boxed{0}$.

The equation becomes $\frac{3}{4} + \frac{a}{4} + \frac{b}{4} = \frac{10}{4}$.

$3 + a + b = 10$.

$a + b = 10 - 3$
$a + b = 7$.
We need two numbers that add up to 7. We can choose $a=3$ and $b=4$.

The completed equation is $\frac{3}{4} + \boxed{\frac{3}{4}} + \boxed{\frac{4}{4}} = \frac{10}{4}$.

The answer is $\boxed{12}$.