We define variables:
x = represent the width of the field
y = represent the length of the field
We write the perimeter (with no fencing along the river):
2400 = 2x + y
We clear y:
y = 2400-2x
Answer:
an expression for the length of the field as a function of x is:
y = 2400-2x
Step 1: Find the value of one variable in terms of the other.

Step 2: Substitute the value you just found for this variable in the other equation.

Step 3: Use your new value for the second variable to find the first.

Now that we know the values for a and b we can find the value of 4a+b.
Answer:
£2.00
Step-by-step explanation:
Badly worded, as they oftena are! But to me it means
30% spent
60% saved (I.e also taken away and put somewhere else)
10% leftover equals 20p
So 20p equals 10% of what she originally had, so 100% must be £2.00, does that make sense?
The expression is 55/5 - 20/4
11-5
the answer is 6