Which value needs to be added to the left polynomial to make it a perfect square trinomial. x^2 - 10x = 3

A)-100

B)100

C)-25

D)20

E)-20

F)25

Each month, a shopkeeper spends 5x + 14 dollars on rent and electricity. if he spends 3x−5 dollars on rent, how much does he spend on electricity? for which value(s) of x is the amount the shopkeeper spends on electricity less than $100? explain how you found the value(s).