13 hours
78.00 ÷ 6.00 equals 13 hours
6×13 equals 78
7x - 5y = 21....(4,?)...so sub in 4 for x and solve for y
7(4) - 5y = 21
28 - 5y = 21
-5y = 21 - 28
-5y = - 7
y = 7/5
check..
7(4) - 5(7/5) = 21
28 - 35/5 = 21
28 - 7 = 21
21 = 21 (correct)
the other coordinate is 7/5......(4,7/5)
Yes, sides AC and AD are congruent and lines BC and DE are also congruent. They also share angle A and bc of the SSA congruence Theorem that means they are congruent.
21 blocks, because if he uses 38 you subtract 17 and you get 21
