Answer:

Step-by-step explanation:
First, note that

And using the chain rule in one variable

Now remember that the chain rule in several variables sates that

Therefore the chain rule in several variables would look like this.

Answer:
$60.
Step-by-step explanation:
Cost price= $50
Selling price = $80
Percentage markup = Gain/Cost price x 100%
=30/50x100
=$60.
You don't define the ratio, so there are two answers:
If 2/3 is boys to girls, then,
2/3 = 24/x
x = 36 girls
If 2/3 is girls to boys, then,
2/3 = x/24
x = 16 girls
Hey I can help. Do u still need it?
89kg in stones would be 12.598 stones