Answer:
800
Step-by-step explanation:
i. find the first four terms,
multiply 20 by 3, multiply the product by 3 and continue
20 × 3 = 60 second term
60 × 3 = 180 third term
180 × 3 = 540 fourth term
20, 60, 180, 540, ...
ii. add the four terms,
20+60+180+540 = 800
