Xy=12
xdy/dx + y = 12
xdy/dx = 12 - y
dy/dx= (12-y) /x
dy/dx | x=-4 ,y=-3 = (12-(-3))/(-4)
= (12+3)/-4 = -15/4
Answer:14
Step-by-step explanation:
A nickel is 5 cents (20% of dollar)
and a quarter is 25 cents (25% of dollar)
We have given a pile of 42 coins worth of $4.90
Let x be the no nickels and
y be the no of quarter
therefore
x+y=42 -----1
+
=4.90 ---2
Solving 
we get
x=14 & y=28
Therefore no of nickels is 14 & no of quarters is 28
Answer:
George is 12, Mary Lou is 24 and Kate is 10.
Step-by-step explanation:
To find these, start by setting George's age as x. This means that we can model Mary Lou's age as 2x, since she is twice as old. We can also model Kate's age as x - 2 since she is two years younger. Now we can add these 3 together and set equal to 46
x + 2x + x - 2 = 46
4x - 2 = 46
4x = 48
x = 12
This means that George is 12.
Mary Lou = 2x
Mary Lou = 2(12)
Mary Lou = 24
Kate = x - 2
Kate = 12 - 2
Kate = 10
Answer:
x = 1/5
y = 6
Step-by-step explanation:
System:
{5x + y = 7
{20x + 2 = y
First equation:
5x + y = 7 -> y = -5x + 7
Plug into second equation:
20x + 2 = -5x + 7
Subtract 2 from both sides:
20x = -5x + 5
Add 5x to both sides:
25x = 5
Divde both sides by 25:
x = 5/25 -> 1/5
~~~~~~~~~~~~~~~~~~~~~~~~~~~`
Come back to the first equation:
5x + y = 7
Plus in our x:
5(1/5) + y = 7
Multiply:
1 + y = 7
Subtract 1 from both sides:
y = 6
Hope this helps, have a nice day! :D
