Hello, cazimi!
Find the area bounded by: the line x  2y + 10 = 0, the xaxis,
the yaxis, and x = 10. I don't suppose you made a sketch . . . Code:

 *(10,10)
 *::
 *:::::
 *::::::::
(0,5)*:::::::::::
* :::::::::::
* :::::::::::
* :::::::::::
 *      +      + 
10  10

We have a trapezoid with: b1 = 5, b2 = 10, h = 10
Use the area formula for trapezoids.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
If we must use Calculus, we have: .y .= .½x + 5
. . . . . . . . . .10
Then: .A .= .∫ (½x + 5) dx
. . . . . . . . . 0