Convert percentages to units.
100% - 20% = 80% = 0.8
100% - 25% = 75% = 0.75
Then multiply those together:
0.8*0.75=0.6=60%
100% - 60% = 40%. That's the overall price percentage reduction.
P.S. You can convert percentages to units by diving % by 100 for example 100% divided by 100 is equal to 1.
And vice versa aka multiply units by 100 and you get %, for example 0.8 times 100 is 80%
Y = 3.5x + 6
Shows the 6 inital fee plus the 3.50 for each pound
The logarithmic expression is

To expand the expression we have to use some properties of logarithm.
We know that 
By using this property we can write,

Square root means to the power 1/2, so for
, we can write
.

Now we have to use another property of logarithm.
We know that, 
So we will use this property to 



Now we have to use another property of logarithm.
We know that, 
By using this property we can write,

This is the required aswer here.
Slope is -9 and y intercept is -6