this is probably more relevant

If the x-axis is going 10mph, the y-axis at 5mph, and the z-axis at 4mph, then after one hour you will reach point $\displaystyle (x_1+10\;,\;y_1+5\;,\;z_1+4)$ where x_1, y_1, and z_1 are the points you started off with.

In other words the formula you will use to find the ending point is: $\displaystyle (x_1+mph\times h\;,\;y_1+mph\times h\;,\;z_1+mph\times h)=(x_2\;,\;y_2\;,\;z_2)$ where h is the time in hours after you started and x_2, y_2, and z_2 are the ending points