Answer:
John's initial investment is Rs.150000
Explanation:
Let the principal amount be a
We are given that John wants to invest in a simple interest savings account .The interest rate on this account is 0.7%.
Now to find simple interest in x years
Formula :

Where P = Principal
T= time
R = rate of interest in decimals
So,

Amount = Principal+Interest
Amount =

We are given that The account balance y can be modeled by the following linear equation y=150,000+150,000(0.007)x
So, On comparing a = 150000
Hence John's initial investment is Rs.150000