Find missing coordinate, when given slope {ACT}

A.) 4
B.) 5
C.) 6
D.) 7
E.) 8

y2 - y1 
---------- = slope of a line
x2 - x1

The points have coordinates of (x1 , y1) and (x2 , y2)

7 - 1            3
-------   =    ----  {substituted given values into slope formula}
k - 1            2

  6           3
-----   =   ----  {subtracted 7 - 1 in first fraction}
k - 1        2

3(k - 1) = 6(2) {cross-multiplied to solve the proportion}
3k - 3 = 12 {used distributive property on left}
3k = 15 {added 3 to both sides}
k = 5 {divided both sides by 3}

B.)  5

- Algebra House