Answer:
r = - 
Step-by-step explanation:
Given that r varies inversely as t , then the equation relating them is
r =
← k is the constant of variation
To find k use the condition t = - 6 when r = - 2, then
- 2 =
( multiply both sides by - 6 )
12 = k, thus
r =
← equation of variation
when t = - 7, then
r =
= - 
Answer:
The selling price of meter of cable must be equal to 3 euros
Step-by-step explanation:
The question in English is
A hardware store buys 4 reels of cable of 200 meters each at 2 euros per meter. How much must the meter sell if you want to earn 800 euros?
we know that
The profit will be equal to the selling price minus the purchase price, all multiplied by the total meters of cable
Let
x -----> the selling price of the meter of cable
y -----> the purchase price of the meter of cable
N ----> the meters of cable
P ----> the profit
so

we have
The total meters of cable N purchased is equal to



substitute

Solve for x
Simplify


therefore
The selling price of meter of cable must be equal to 3 euros
15 minutes is 25% of an hour. You can tell this because there are exactly 4 15 minute periods in one hour.
Hope this helped.