we know that
The sum of the interior angles in any polygon is equal to
S=180(n-2)
where
n is the number of sides
In this problem we have a quadrilateral
so
n= 4 sides
substitute in the formula
S=180(4-2)
S=180(2)
S=360 degrees
That means
3x+x+2x+x+10=360
solve for x
7x+10=360
7x=350