3x – 7 = 2x + 8
4(7x + 10) = 3(9x – 5) + 20
Ricardo is 4 years less than twice as old as his sister. The sum of their ages is 20. How old is Ricardo?
A television is marked down from $350 to $308. What is the discount rate?
–3(x + 1) = 2(x – 8) + 3
2006-11-25 15:29:48 · 6 answers · asked by mslivinglarge 1 in Science & Mathematics ➔ Mathematics
There've already been a lot of good answers, but I thought I'd see if I could explain it a little more clearly.
1) 3x - 7 = 2x + 8. Start by adding 7 and subtracting 2x from each side: 3x -7 +7 -2x = 2x +8 +7 -2x. Combine the terms to get x = 15.
2) 4(7x + 10) = 3(9x - 5) + 20. Start by multiplying 4 by everything in the first set of parentheses and 3 by everything in the second set: 28x + 40 = 27x - 15 + 20. Now, subtract 27x and 40 from each side: 28x - 27x +40 -40 = 27x - 27x -15 +20 - 40. Combine the terms to get x= -35.
3) Let Ricardo's age = R and his sister's = S. We are told that R = 2S - 4 and R + S = 20. Since R and 2S - 4 are the same, we can write the second equation as 2S - 4 + S = 20. Add 4 to each side and combine: 3S = 24. Then divide by 3: S = 8. So his sister is 8 years old. Remember that their ages added together are 20, so he must be (20 - 8) = 12 years old.
4) First, find the actual amount of the discount. The original price was $350, and the sale price is $308, so the discount is ($350 -$308) = $42. Now, you want to find the rate of discount, or what percent of the price was taken off. To find that, you divide the discount ($42) by the original price ($350) and mutiply by 100%. It comes out to 12%.
5) -3(x + 1) = 2(x - 8) + 3. Start by multiplying out the parentheses: -3x -3 = 2x - 16 + 3. Then subtract 2x and add 3 to each side and combine the terms: -5x = -10. Divide by -5: x = 2.
2006-11-25 15:55:28 · answer #1 · answered by Amy F 5 · 1⤊ 0⤋
#3.) Ricardo is 12. His sister is 8
4 years less than 2x 8 =12
12+8 = 20!
#4.) x($350) = (350-308)
x = 0.12, thus 12%
2006-11-25 15:36:38 · answer #2 · answered by diidy 3 · 1⤊ 0⤋
1. x= 15 (move all x's to one side and all constants to other and divide to get 1 x).
2. x= -35 ( distribute and do the same as #1)
3. sister is 8 years old. ricardo is 12. ( let x = sister, let 2x-4 = ricardo ; x+2x-4=20. )
4. 12% discount
5. x=2 ( same as one and two.)
2006-11-25 15:41:34 · answer #3 · answered by Jen M 2 · 1⤊ 0⤋
All I know is the TV markdown is 12%. and the sister is 8 and Ricardo is 12.
2006-11-25 15:34:51 · answer #4 · answered by besitos2610 5 · 0⤊ 0⤋
1) x=15
2) x=-35
3) Ricardo is 12
4) 120%
5) x=2
2006-11-25 15:45:49 · answer #5 · answered by Peanuts Suck 2 · 1⤊ 1⤋
You go girl!
Good luck!!
2006-11-25 15:37:56 · answer #6 · answered by DREAMY 2 · 0⤊ 0⤋