The expression given is k = am + 3mx. To find the value of m in terms of a, k, and x, we need to isolate m. We can start by rearranging the equation: k - 3mx = am. Then, we can divide both sides by a to get m = (k - 3mx)/a. This can be simplified to m = k/a - 3x. Therefore, the value of m in terms of a, k, and x is k/a - 3x.