The answer is 36
Answer - 36
I hope this helps you
Pythagorean
hypothenus ^2=base^2+height ^2
hypothenus ^2=15^2+20^2
hypothenus ^2=225+400
hypothenus ^2=625
hypothenus ^2=25
3x - 2y = 1
2x + 2y = 4
Add the second equation to the first
5x = 5
2x + 2y = 4
Divide the first equation by 5
x = 1
2x + 2y = 4
Subtract the first equation from the second
x = 1
x + 2y = 3
Subtract the first equation from the second again
x = 1
2y = 2
Divide the second equation by 2
x = 1
y = 1
<h3>
So, the solution is x = 1 and y = 1 {or: (1, 1)} </h3>
Answer:
Mostly correct
For Q3, you are doing great, you remembered that negative numbers can happen if the exponent is an odd number.
For Q4, I think you were confused with the fractions,
4(i)

4(ii) is also wrong but I'll let you try to fix it yourself following what I given you for 4(i). You should get 1/64
Hope this helps!
1.50x + 450 = 3x
450 = 3x - 1.50x
450 = 1.50x
450/1.50 = x
300 = x
300 copies must be sold to break even