Answer:
 after 10days savannah will have 31 pennies
Explanation:
arithmetic progression (AP)
(a1) started with, 5 pennies 
common difference (d), 3 pennies 
formula: Tn = a + (n-1)d
 
after 10 days, T10 = 5 + (10- 1)(3)
T10 =5 + 27
T10= 31 
therefore after ten days savannah has 31 pennies