A few area questions

Please help! :)
What is the area of...
1. A rhombus with sides of length 13 and a diagonal of length 10.
2. A parallelogram with base 2x and corresponding height x (give your answer is terms of x).
3. A trapezoid with bases of lengths 20 and 24 and with height 9.

1) for the other diagonal:

let the two equal parts of this diagonal =x

x²+5²=13² =>x=12

the other diagonal is 24 so:

S = (a*b)/2 => 10*24 / 2 => 120

2) area of a parallelogram is:

b*h so 2x*x =2x²

3) area of a trapezoid is:

(a+b)*h / 2 so:

(20+24)*9 / 2 =>198

4) this triangle is a right triangle as 8²+15²=17²

area of a triangle is:

(b*h)/2 => 8*15 / 2 =>60