Equilateral Triangle Algebra Question

Question

Find the value of x and y in this equilateral triangle. (There is a picture of an equilateral triangle. On the left side it is 26cm, on the right side it is x + 3y cm and on the bottom is 4x-y cm)

Answer 1

26=x+3y

26=4x-y

multiply the second equation by 3

78=12x-3y

add the first and new second equations

26=x+3y

78=12x-3y

104=13x

x=104/13

x=8 cm

26=8+3y

26-8=3y

18=3y

y=18/3

y=6 cm