A rhombus is a parallelogram with four equal-length sides. A square is a rectangle with four equal-length sides.

A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

A line segment is a portion of a line with a measurable length. The midpoint of a line segment is the point exactly halfway between the endpoints. The midpoint bisects (cuts in half) the line segment.

You need to find the value of c so solve the first equation in terms of x:

9c + x = 5
x = 5 - 9c

then substitute the result (5 - 9c) into the second equation:

-c - 9(5 - 9c) = 6
-c + (-9 x 5) + (-9 x -9c) = 6
-c - 45 + 81c = 6
-c + 81c = 6 + 45
80c = 51
c = \( \frac{51}{80} \)
c = \(\frac{51}{80}\)

The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 9 x 2) + (2 x 2 x 3) + (2 x 9 x 3)
sa = (36) + (12) + (54)
sa = 102