Step-by-step explanation:
If the tens digit of the number is X and the ones digit is Y then the number is equal to 10*X + Y
If you reverse the digits then the number is equal to 10*Y + X
If reversing the digits decreases the number by 36 then
10*Y + X = 10*X + Y - 36
The sum of the digits is 4 so X + Y = 4 ==> X = 4 - Y
Substitute this value of X into the 1st equation
10*Y + (4 - Y) = 10*(4 - Y) + Y - 36
9*Y + 4 = 40 - 9*Y - 36
18*Y = 0
Y = 0
I hope it helps you
So X = 4 - 0 = 4 and the number is 40
so, let's check 40 - 04 = 36
Using the product rule, we have

so that

The equation of the tangent line to <em>W(x)</em> at <em>x</em> = 7 has all the information we need to determine <em>m'</em> (7).
When <em>x</em> = 7, the tangent line intersects with the graph of <em>W(x)</em>, and
<em>y</em> = 4.5 + 2 (7 - 7) ==> <em>y</em> = 4.5
means that this intersection occurs at the point (7, 4.5), and this in turn means <em>W</em> (7) = 4.5.
The slope of this tangent line is 2, so <em>W'</em> (7) = 2.
Then
