Answer:
x=10, y=5
Step-by-step explanation:
For substitution, you always want to get the variable alone. The second equation (x-2y=0) will be easier to substitute into the first equation.
x-2y=0
x=2y
You can substitute 2y as x on the first equation (x+4y=30).
2y+4y=30
6y=30
y=5
Plug y=5 into any equation.
x+4(5)=30
x+20=30
x=10
3/10+ 5/8
First find a common denominator
multiply top and bottom the same
12/40 +25/40
add
37/40
You need to know and have memorized metric unit conversions. They are easy, you just need to know how many zeros to add.
1 cm = 10 mm
1 m = 1000 mm
1 m = 100 cm
1 km = 1000 m
(1.) 4m + 3cm = 400cm + 3cm = 403cm
(2.) 3km + 8m = 3000m + 8m = 3008m
(3.) 7cm + 9mm = 70mm + 9mm = 79mm
(4.) 1m + 5cm = 100cm + 5cm = 105cm
(5.) 5km + 5m = 5000m + 5m = 5005m
Do you see that to switch 5km to smaller unit meters you just add the zeros on to the end. Because 1km = 1000m ; 5km = 5000m
You try the rest. let me know if you have any questions.
Answer:
9 mph = the speed in still water
Step-by-step explanation:
Let r = the speed in still water
Then the speed going down stream is r + 3
and the speed going upstream is r - 3
d = rt or t = d/r
time going downstream is 16/(r + 3) and time going upstream is 16/(r - 3)
The total time was 4 hours, so
Multiply thru the equation by (r + 3)(r - 3)
Then 16(r - 3) + 16(r + 3) = 4(r + 3)(r - 3)
16r - 48 + 16r + 48 = 
- 36
- 36 = 32r
- 32r - 36 = 0
4(r - 9)(r + 1) = 0
r = 9 or -1
But a rate of speed cannot be negative, so x ≠ -1
So, r = 9 mph = the speed in still water
Answer is X=-0.206
Hope this helps
Have a great night or day
