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 7 x 1) + (2 x 1 x 3) + (2 x 7 x 3)
sa = (14) + (6) + (42)
sa = 62

A triangle is a three-sided polygon. It has three interior angles that add up to 180° (a + b + c = 180°). An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite (d = b + c). The perimeter of a triangle is equal to the sum of the lengths of its three sides, the height of a triangle is equal to the length from the base to the opposite vertex (angle) and the area equals one-half triangle base x height: a = ½ base x height.

According to the Pythagorean theorem, the hypotenuse squared is equal to the sum of the two perpendicular sides squared:

c² = a² + b²
c² = 6² + 3²
c² = 36 + 9
c² = 45
c = \( \sqrt{45} \)

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

-5c + x = 4
x = 4 + 5c

then substitute the result (4 - -5c) into the second equation:

-7c - 2(4 + 5c) = -1
-7c + (-2 x 4) + (-2 x 5c) = -1
-7c - 8 - 10c = -1
-7c - 10c = -1 + 8
-17c = 7
c = \( \frac{7}{-17} \)
c = -\(\frac{7}{17}\)

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.