You need to use the slope intercept form of equations, hence you need to isolate y to the left side in both equations such that:

`-ky = -3x - 7 =gt y = (3/k)x + 7/k`

`2y = -tx + 3 =gt y = (-t/2)x + 3/2`

You need to identify the slopes of both lines such that:

`m_1 = 3/k ; m_2 = -t/2`

You need to write the relation between the slopes of two orthogonal lines such that:

`m_1*m_2 = -` `1`

`(3/k)*(-t/2) = -1 =gt 3/k = 1/(t/2)`

`3/k = 2/t =gt 2k = 3t =gt k = 3t/2`

Hence, evaluating the relation between k and t if the lines are orthogonal yields  `k = 3t/2` .