Use proportions for all of them, for #1 use the proportion 12/30 = 9/a based on corresponding sides and then cross multiply. a=22.5 For #2 use the proportion y/35 = 64/40 based on corresponding sides and then cross multiply, y=56 For #3 use the proportion 42/? = 54/36 and then cross multiply, ?=28
It's <span>Diophantine equation.
First, we need to found gcd(6,(-2)):</span>
6=2*3
(-2)=(-1)*2
So, gcd(6,-2)=2
Now, the question is. Can we dived c=24, by gcd(6,-2) and in the end get integer?
Yes we can.

So, we can solve it.
Now is the formula:

Second, we need the first pair (x0,y0)
if
x=0
then

Third, we gonna use that formula:

Congratulations! We solve it.
Answer:
1. 4; 2. 32; 3. 9; 4. 8; 5. 12; 6. 16; 7. 6; 8. 8; 9. 8; 10. 8
N(3)-8=16
add 8 to both sides
3n=24
Divide each side by three
n=8