Answer:
[tex] {1.2}^{n} \times 2.5[/tex]
Step-by-step explanation:
it's simple my dear friend.
first, she runs 3 miles per week.
so in
[tex] {a}^{(n - 1)} \times b[/tex]
b is 3. the initial value.
increasement by 20% means she runs 1.2 times than before.
[tex] \frac{100 + 20}{100} = \frac{120}{100} = \frac{12}{10} = 1.2[/tex]
then a=1.2
so we have now:
[tex] {1.2}^{(n - 1)} \times 3 \\ = {1.2}^{n} \times \frac{3}{1.2} \\ = {1.2}^{n} \times 2.5[/tex]
and we got it!