please help 10 points?

Question

1: What number, when added to the numerator and denominator of 3/7, changes 3/7 into a fraction equivalent to 7/9?
7
11
12
13


2: What number, when added to the numerator and denominator of 11/15, changes 11/15 into a fraction equivalent to 4/5?
2
3
4
5


3: What number, when added to the numerator and denominator of 1/8, changes 1/8 into a fraction equivalent to 3/4?
10
12
20
22


4: A boat can travel at 10 mph in still water. It travels 75 miles downstream with the current in the same time it travels 25 miles upstream. What is the speed of the current?
5 mph
6 mph
7 mph
12 mph


5: This airplane would travel 350 mph in still air. However, airplanes always travel on air currents. With the air current, the airplane travels 1120 miles in the same time that it travels 980.1 miles against the air current. Find the speed of the air current. (This is just like the water current problems.)
17.8 mph
23.3 mph
26 mph
27.6 mph

Answer 1

1: (3 + x) / (7 + x) = 7/9
3 + x = 7/9 * (7 + x)
3 + x = 49/9 + 7/9x
2/9x = 22/9
x = 11 answer

2: (11 + x) / (15 + x) = 4/5
11 + x = 12 + 4/5x
1/5x = 1
x = 5 answer

3. (1 + x) / (8 + x) = 3/4
1 + x = 6 + 3/4x
1/4x = 5
x = 20 answer

4. (10 + x) / 75 = (10 - x) / 25
10 + x = 30 - 3x
4x = 20
x = 5 answer

5. (350 + x) / 1,120 = (350 - x) / 980.1
350 + x = 400 - 1.1427405x
2.1427405x = 50
x = 23.3 answer

Answer 2

11 => 14/18 = 7/9

5 => 16/20 = 4/5

20 => 21/28 = 3/4

(10 - x)t = 25; (x +10)t = 75 = 3 x 25 = 3 (10 - x) t
so x + 10 = 30 - 3x; 4x = 20
x = 5

(350 - x)t = 980.1 ; (350 + x )t = 1120 => t = 1120 / (350 + x)
1120(350 - x ) = 980.1(x +350)
392,000 - 1120x = 980.1x + 343.035
2000.1x = 48,965
x = 23.3155 ??

Answer 3

4. Let X = current speed T = time

When the current is against you (upstream, subtract current speed from still water. Going downstream, add current speed.

t(10-x) = 25
t(10+x) = 75
3t(10-x) = t(10+x)
3(10-x) = 10+x
30-3x = 10+x
20 = 4x
x = 5

Answer 4

here they are, oh and its not a good idea to get people to do your homework but if its not homework thats ok

1 = 11

2 = 5

3 = 20

4 = ???

5 = ???


thats hard...im only in 6th but i'm in 7th enriched math and i know for a fact the first 3 are right

Answer 5

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Answer 6

1. 11
2. 5
3. 20
I can't get the other two, sorry.