Change into improper fraction
take 3 x 25+18 divided by 25=93\25
93\25=3.72
I'm not sure what you mean by difference, so I am guessing you meant to write "distance". If this is not the case, then feel free to report me. Anyway, to find the distance between two points you would use the distance formula.
Distance Formula: 
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Let's substitute our point coordinates into the formula. We'll substitute -1 and 6 for x_2 and x_1, and 14 and 16 for y_2 and y_1. After substituting, your formula will now look like: 
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Subtract the coordinates.
Square the subtracted coordinates.
Add 49 and 4.
Square root 53 and round the answer to the nearest tenth.
7.28 becomes 7.3.
7.3 units is the distance between points M and Z.
We will form the equations for this problem:
(1) 1100*y + z = 113
(2) 1500*y + z = 153
z = ? Monthly administration fee is notated with z, and that is the this problem's question.
Number of kilowatt hours of electricity used are numbers 1100 and 1500 respectively.
Cost per kilowatt hour is notated with y, but its value is not asked in this math problem, but we can calculate it anyway.
The problem becomes two equations with two unknowns, it is a system, and can be solved with method of replacement:
(1) 1100*y + z = 113
(2) 1500*y + z = 153
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(1) z = 113 - 1100*y [insert value of z (right side) into (2) equation instead of z]:
(2) 1500*y + (113 - 1100*y) = 153
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(1) z = 113 - 1100*y
(2) 1500*y + 113 - 1100*y = 153
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(1) z = 113 - 1100*y
(2) 400*y + 113 = 153
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(1) z = 113 - 1100*y
(2) 400*y = 153 - 113
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(1) z = 113 - 1100*y
(2) 400*y = 40
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(1) z = 113 - 1100*y
(2) y = 40/400
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(1) z = 113 - 1100*y
(2) y = 1/10
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if we insert the obtained value of y into (1) equation, we get the value of z:
(1) z = 113 - 1100*(1/10)
(1) z = 113 - 110
(1) z = 3 dollars is the monthly fee.
