Triangle ABC is an equilateral triangle in which AB = (3x + 1)cm, BC = (2x + 3y +5)cm and AC = (x + 9y +6)cm. Find the values of x, y and the side of the equilateral triangle.

We have,AB = 3x+1 cm; BC = 2x+3y+5 cm; CA = x+9y+6 cmSince, ABC is an equilateral , thenAB = BC = CANow, AB = BC3x + 1 = 2x + 3y + 5x - 3y = 4   ....1Now, BC = CA2x + 3y + 5 = x + 9y + 6x - 6y = 1    ......2Subtracting 2 from 1, we get3y = 3   y = 1Put y = 1 in 1, we getx - 3×1 = 4x = 7Now, AB = 3x + 1 = 3×7 + 1 = 22 cmNow, BC = 2x+3y+5 = 2×7+3×1+5 = 14 + 3 + 5 = 22 cmNow, CA = x + 9 y + 6 = 7 + 9×1 + 6 = 22 cm

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AB = BC = AC

AB = BC
3x + 1 = 2x + 3y + 5 
3x - 2x - 3y = 5 - 1 
x - 3 y = 4 → 1 

BC = AC
2x + 3y + 5 = x + 9y + 6 
2x + 3y - x - 9y = 6 - 5
x - 6y = 1 → 2

Subtracting 1 from 2
x - 6y - x + 3y = 1 - 4 = -3 
-3y = -3 
y = 1 

Substituting y = 1 in 1 
x = 7
Side = 22 cm
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