A quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².

You need to find the value of a so solve the first equation in terms of y:

5a + y = -5
y = -5 - 5a

then substitute the result (-5 - 5a) into the second equation:

-5a + 9(-5 - 5a) = -9
-5a + (9 x -5) + (9 x -5a) = -9
-5a - 45 - 45a = -9
-5a - 45a = -9 + 45
-50a = 36
a = \( \frac{36}{-50} \)
a = -\(\frac{18}{25}\)

A cylinder is a solid figure with straight parallel sides and a circular or oval cross section with a radius (r) and a height (h). The volume of a cylinder is π r²h and the surface area is 2(π r²) + 2π rh.

The area of a trapezoid is one-half the sum of the lengths of the parallel sides multiplied by the height:

a = ½(b + d)(h)
a = ½(4 + 9)(3)
a = ½(13)(3)
a = ½(39) = \( \frac{39}{2} \)
a = 19\(\frac{1}{2}\)