Greg is saving up his money to buy a new phone. The amount of money he has after any given week (w) can be given by the equation M = 90 + 15w. How many weeks will it take Greg to save up the $210 he needs to buy the phone?

It will take Greg 8 weeks to save up to buy the phone.

Step-by-step explanation:

Given equation is:

M = 90 + 15w

Here,

M represents the money saved

w represents the number of weeks

Greg wants to save 210

Putting M = 210 in the given equation;

210 = 90 + 15w

210 - 90 = 15w

15w = 120

Dividing both sides by 15

Hence,

It will take Greg 8 weeks to save up to buy the phone.

see explanation

step-by-step explanation:

since the sequence is geometric there is a common ratio r between consecutive terms, that is

r = 4 ÷ - 2 = - 2

r = - 8 ÷ 4 = - 2

r = 16 ÷ 8 = - 2

the next term - 13 must be incorrect as it should be - 32 for the sequence to be geometric.

the first 4 terms are therefore geometric with common ratio r = - 2