Rule: X △ y = 3x-2y, known x △ 4 △ 1 = 7, find the ratio of X

Rule: X △ y = 3x-2y, known x △ 4 △ 1 = 7, find the ratio of X

x△(4△1)=x△(3×4-2×1)=x△(12-2)=x△10=3x-2×10=3x-20=7
There is an equation
3x-20=7
3x=7+20
3x=27
x=27÷3
x=9