Answer: the fixed amount that Daria earns for each television is $50
Explanation:
Let x represent the fixed amount that Daria earns for each television.
She earns a fixed amount for each television and an additional $15 if the buyer gets an extended warranty. Assuming she sells y televisions, her total earnings would be
xy + 15y
Daria sells 11 televisions with extended warranties, she earns $715. This means that
11x + 15 × 11 = 715
11x + 165 = 715
11x = 715 - 165
11x = 550
x = 550/11
x = 50