Answer:
We are given that the length of side BC is congruent to AB so they have an equal measure. Based on this we can make an equation where their lengths are equal, and then solve for x:
2x - 6 = x + 17
x - 6 = 17
x = 23
Now we can plug x into the expression 2x - 6:
BC = 2(23) - 6
BC = 46 - 6
BC = 40
Explanation: