If this is an equilateral triangle, we need half of it to find the height which is a leg of a right triangle with a hypotenuse of 15. That means that the base of this half triangle is 7.5. Use Pythagorean's Theorem to fine the height.

. x = 12.99 or 13
Answer:
hope this helps you look it once.
When it says 4x4 and 12x2 does that mean it’s squared or multiplied by those?
S = 9C
first sentence written as an expression
Where S represents the angles supplement
and C represents the angles complement
A + S = 180
definition of supplementary allows me to make this statement Where A is the original angle
A + C = 90
definition of complimentary allows this statement
now add the prior 2 statements together
A + S + A + C = 180 + 90
now simplify
2A + S + C = 270
now replace S with 9C using first statement
2A + 9C + C = 270
now simplify
2A + 10C = 270
now divide both sides by 2
A + 5C = 135
now using the second statement isolate A by adding C to both sides
A = 90 - C
now combine the two prior statements
90 - C + 5C = 135
now simplify
90 + 4C = 135
now subtract 90 from both sides
4C = 45
now divide both sides by 4
C = 11.25
so the complimentary angle is 11.25
now take the third equation and substitute in C
A + 11.25 = 90
now subtract 11.25 from both sides
A = 78.75
so the original angle is 78.75
now use the second equation and substitute in A
78.75 + S = 180
now subtract 78.75 from both sides
S = 101.25
so the suplimentary angle is 101.25