Answer:
x = 8
base angle = 81 deg
Explanation:
we observe that because the given triangle is a isosceles triangle, the base angles must be the same.
Hence the missing base angle must also be (10x+1)°
recall that all internal angles of an triangle must add up to 180 deg,
hence
180° = sum of all internal angles
180° = 18° + (10x+1)° + (10x+1)°
180° = 18° + 2(10x+1)° (subtracting 18 from both sides)
180 - 18 = 2(10x+1)
162 = 2(10x+1) dividing both sides by 2)
162 / 2 = 10x + 1
81 = 10x + 1 (subtracting 1 from both sides)
81 - 1 = 10x
10x = 80 (divide both sides by 10)
x = 80/10
x = 8 (answer)
substituting x = 8 into the expression for the base angle
base angle = (10x+1)
= 10(8) + 1
= 10 + 1
= 81