In which expression should the exponents be multiplied
a.2^9 over 2^7
b.(6^10)^-7
c.(1 over 2)^3 (1 over 2)^5
d.5^2 . 5^4

With finding limits of multi variable !

New york is the 27th largest state in the united states.what percent of the 50 states in the us are larger than new york

Ben frank is an electrician who installs lighting fixtures. he charges (in dollars) his clients 15h+40f15h+40f where hh is the number of hours worked and ff is the number of fixtures installed. how much does ben frank charge when he works 77 hours and installs 99 fixtures?