The final answer for this is 4x^2-25y^2.
Answer:
day 540
Step-by-step explanation:
He increases his number of situps by 2 each day meaning on day 1 he'd do 2 extra, on day 2 he'd do 4 extra, on day he'd do 6 extra etc. We can show this by saying +2x where x is the day he is on. Then since he started with 20 we have to add 20 so it would be 20+2x. We want to know what day it is when he does 1100 situps so we can set our equation equal to 1100 and solve for X which is the day it would be.
20+2x=1100
2x=1080
I hope this helps and please don't hesitate to ask if there is anything still unclear!
x=540

=

equals
k = 15.6
First, simplify

to 1.2. Your problem should look like:

= 1.2
Second, multiply both sides by 13. Your problem should look like: k = 15.6, which is the answer.
Answer:
25X + 25Y = 1700
25X + 100Y = 3200
Step-by-step explanation:
Given that the principal of a high school spent $1700 for X desk and Y chairs at $25 each. Then, the equation will be
25X + 25Y = 1700 ....... (1)
If he had bought half the number of desk in twice the number of chairs he would have spent 1600. That is
25(X/2) + 25(2Y) = 1600
25X/2 + 50Y = 1600
Find the LCM and cross multiply
25X + 100Y = 3200 ........(2)