Don’t know how to solve.

Answer:
$122.88
Step-by-step explanation:
the phone decreases by 20% each year , that is
(100 - 20)% = 80% = [tex]\frac{80}{100}[/tex] = 0.8
the phone reduces by a factor of 0.8 each year , then after 4 years
value = $300 × [tex](0.8)^{4}[/tex] = $122.88