this is an addition of powers .
on sunday , Margos dad gives 5c, we will represent it as 5^1
therefore: sunday 5^1
Monday 5^1 x ( 5^1)
because bases are the same , we add exponents
this means that 5^1(5^1) = 5^2
Tuesday 5^2(5^1) = 5^3
wednesday 5^3(5^1) = 5^4
thursday 5^4( 5^1)= 5^5
Friday 5^5(5^1)= 5^6
saturday 5^6 (5^1)= 5^7