Since Mike drove at 65 mph for 3 hours, we have that he traveled:
![3\cdot65=195\text{ miles}](https://img.qammunity.org/2023/formulas/mathematics/college/b5s1l3nyqup7gbri4wa8ew9mhqvlv59p44.png)
for Sandra, we have the following:
![3\cdot70=210\text{ miles}](https://img.qammunity.org/2023/formulas/mathematics/college/4iyxpuwmd7tt9hcpl6dkwwi7fod5o1hgra.png)
notice that both trajectories with the distance apart segment form a right triangle, then, using the pythagoren theorem, we get:
![x=\sqrt[]{(210)^2+(195)^2}=\sqrt[]{44100+38025}=\sqrt[]{82125}\approx287\text{ miles}](https://img.qammunity.org/2023/formulas/mathematics/college/miw475a9stajcaq4865sxg5e9zt9qtogtz.png)
therefore, Sandra and Mike are approximately 287 miles apart after 3 hours