Help pls someone!? Pls

He has been doing sit ups for 9 days

Step-by-step explanation:

lets do this: y = amount of sit ups, x = number of days

The equation would be:

y = 2x + 15     (let me know if you don't understand how I got this)

Now, to see how many days it took him to reach 33 sit ups, set y = 33 and plug it into the equation:

33 = 2x + 15   ⇒ subtract 15 from each side

18 = 2x   ⇒ divide each side by 2

x = 9

225x²+4=0

225x²=0-4

225x²=-4

x²=-4/225

x=±√-4/225