By the given information, we know that Jack type at a rate of 70 words in 2 minutes, 70/2:
[tex]\frac{70\text{ words}}{2\text{ minutes}}=35\frac{\text{words}}{\text{minute}}[/tex]Which simplified gives us a rate of 35 words per minute.
How many minutes is Jack going to take to type 350 words:
[tex]350\text{ words}\times\frac{1\text{ minute}}{35\text{ words}}=10\text{ minutes}[/tex]