Answer and workings in the attachment below. Also, do me one big favour. Let me know if it's the answer your teacher or text book ends up giving you. That would give me some satisfaction.
Answer: 80%
After x weeks:
Jules will have: 1,200 + 40 x.
Kelsey will have: 400 + 50 x.
If we want to know in how many weeks will they have the same amount of money, we will make an equation:
400 + 50 x = 1,200 + 40 x
50 x - 40 x = 1,200 - 400
10 x = 800
x = 800 : 10
x = 80
Answer: In 80 weeks they will have the same amount of money.
Answer id provided in the image attached.
Cos(x)= adjacent/hypotenuse
cos(18)=x/25 (cross multiply)
25*cos(18)=x
x= 23.78 cm <--- this is rounded to the nearest hundredth.