Answer:
Sandy needs to babysit for 35 hours to earn enough money to buy an Iphone.
Explanation:
Sandy gets $100 advance pay and $10 per hour for babysitting.
Let x denotes the number of hours then
10x + 100
Sandy wants to buy an Iphone for $450
10x + 100 = 450
Solving the above equation
10x = 450 - 100
10x = 350
x = 350/10
x = 35 hours
Therefore, Sandy needs to babysit for 35 hours to earn enough money to buy an Iphone.