In standard form, slope is always the negative of the x coefficient over the y coefficient.
If you dont want to have that memorized, you can use algebra to get the equation of the line into slope-intercept form (y=mx+b)
Set it equal to y
2x - 5y = 6
2x = 5y + 6
2x - 6 = 5y
(2/5)x - 6/5 = y
Now it is in slope intercept form. In slope intercept form, the coefficient multiplying with x is the slope of the line. Therefore, the slope equals 2/5.
V = lwh
48 = 8 x 2 x h = 16h
h = 48/16 = 3
height = 3 inches.
Try this solution:
let the unknown two-digits number be 'xy'.
Then it is possible to write any two-digit number as 10x+y, where x - the tens digit and y - the unit digit.
Using the rule described above the phrase 'the tens digit of a number is twice the units digit' may be written as x=2y.
Using the same rule the phrase 'if the digits are reversed, the new number is 36 is less than the original number' may be written as (10x+y)-(10y+x)=36.
These two equations may be resolved as system of two equations:

Check: the original number is 84, the new number is 48; difference is 84-48=36.
answer: 84