The interior angles of a triangle are

[Diver]

So, given the full question, my answer is invalid.

x=0, y=10, x+y = 10 = invalid

[SupremeSpod]

Would the answer be one of the following;

A 15
B 14
C 13
D 12
E 11

If that's "rule of thumb", it's no wonder you keep trying to sever yours!

[TimberWolf]

So, given the full question, my answer is invalid.

Yes, it appears that 0 isn't a positive integer (based on a two second search).

[Doggy Styles]

That's one thing the Romans DIDN'T do for us - give us a bloody zero.

[SimonMac]

What is x+y?

The 24th and 25th letters of the traditional English alphabet

[SimonMac]

(duplicate post)

[KentPhilip]

I can't work it out. Can someone post the solution, with workings?

[mudskipper]

I can't work it out. Can someone post the solution, with workings?

http://www.mathcomp.leeds.ac.uk/b_file.php?id=469

Q25

[OwlHoot]

I can't work it out. Can someone post the solution, with workings?

k2p2 posted a link to the solutions, but one can solve it in a slightly different way (although much the same in principle)

(5x + 3y) + (3x + 20) + (10 y + 30) = 180 gives 8x + 13y = 130, i.e. 8(x + y) = 5(26 - y)

Because 5 is prime relative to 8, it must divide x + y, which is say 5z, giving 8z = 26 - y, i.e. 13z = 26 + x (adding x + y (= 5z) to both sides)

But that means 13 must divide x, which is say 13t, so that (13t + y) = 5(2 + t), i.e. y = 10 - 8t, which for positive x and y forces t = 1.

[Diver]

Stopit OwlHoot, you'll confuse the boy