I'd start by writing an equation for each of the right triangles. (Pythagorean theorem)
y² + 9² = z²
x² + z² = (4+9)²
4² + y² = x²
we want to find z so combine the equations by substituting the other variables x,y out.
substitute y² for (x² - 4²) in 1st equation.
(x² - 4²) + 9² = z²
now by rearranging the 2nd equation we can substitute x² for (13² - z²)
(13² - z²) - 4² + 9² = z²
169 - z² - 16 + 81 = z²
234 - z² = z²
234 = 2z²
234/2 = z²
117 = z²
√(117) = z
√(9*13) = z
3√(13) = z
13 goes in the box
11) Since the triangle has a pair of congruent base angles, it is an isosceles triangle which means that the two pairs of legs are congruent.
Make them equal to each other in an equation.
5x = x + 20
Subtract x from both sides.
4x = 20
Divide both sides by 4.
x = 5
12) The two legs are congruent so that means the base angles must be congruent. First find the measure of the base angles. Create an equation:
x + x + 50 = 180
Combine like terms.
2x + 50 = 180
Subtract 50 from both sides.
2x = 130
Divide both sides by 2.
x = 65
Now make the base angle plus x equal 180, because they form a straight line.
65 + x = 180
Subtract 65 from both sides.
x = 115
13) You know the vertex angle (top angle) is 90 degrees because it is supplementary to a right angle. The triangle is isosceles because the two legs are congruent, so make the base angles plus 90 add up to 180 in an equation.
x + x + 90 = 180
Combine like terms.
2x + 90 = 180
Subtract 90 from both sides.
2x = 90
Divide both sides by 2.
x = 45
31.5% of 473 can be calculated as follows
(31.5/100) * 473
= 14899.5/100
= 148.99
hope it helped
