Answer:
20 units
Step-by-step explanation:
the perimeter = 7+4+4+5 = 20 units
Answer: 
Step-by-step explanation:
Given
The temperature on Monday was 
By Tuesday, it becomes 
Change in temperature is the difference between the two temperatures.

Therefore, the change in temperature is
.
The equation given in the question has two unknown variables in the form of "x" and "y". The exact value of "x" and "y" cannot be determined as two equations are needed to get to the exact values of "x" and "y". This equation can definitely be used to show the way for determining the values of "x" in terms of "y"and the value of "y" in terms of "x". Now let us check the equation given.
2x - 5y = - 15
2x = 5y - 15
2x = 5(y - 3)
x = [5(y - 3)]/2
Similarly the way the value of y can be determined in terms of "x" can also be shown.
2x - 5y = - 15
-5y = - 2x - 15
-5y = -(2x + 15)
5y = 2x + 15
y = (2x +15)/5
= (2x/5) + (15/5)
= (2x/5) + 3
So the final value of x is [5(y -3)]/2 and the value of y is (2x/5) + 3.