Answer shown and explanation above! Hope this helps!
Answer:
1300
Step-by-step explanation:
Let the amount put in the station's tank = x
4(400 + x) = 8100 - x Remove the brackets
1600 + 4x = 8100 - x Subtract 1600 from both sides
1600 - 1600 + 4x = 8100 - 1600 - x Do the subtraction
4x = 6500 - x Add x to both sides
4x + x = 6500 - x + x
5x = 6500 Divide by 5
5x/5 = 6500/5
x = 1300
1300 gallons were added to the station's tank.
Usually you are given more information about the rectangle such as distance of length in terms of width.
You know that the formula for perimeter is
P=2(l+w)
Substitute p and the other values to find width.
Hope I helped :)
