Answer:
x=20 cm
Step-by-step explanation:
Let x be the length of equal sides.
Area of triangle=
We have to find the values of x.
We know that
Area of right triangle=
Where b=Base of triangle
h=Height of triangle
Using the formula
Area of right triangle=





Hence, the value of x=20 cm
7x +2y +4 is the simplified form of this expression.
If you notice the picture below
the composite figure is just a trapezoid sitting on top of a rectangle
and then, the rectangle has a triangular hole in it
so.. get the area of the trapezoid

then get the area of the rectangle, which is just a 12x14
and then get the area of the triangle, which surely you know is 1/2 bh
then, subtract the triangle's area from the rectangle's area
and whatever is left, namely the difference, add that to the area of the trapezoid, and that's the composite's area
namely the area of the trapezoid plus the rectangle's, minus the triangle's
This is the answer hopefully I helped as soon as possible