You'll have to set this up as two separate problems. First, we want to take 15% off the original $20 bill. To do this, you're going to multiply 20 by .15, which gives you $3. So, 15% off $20 is $17.
Now, we want to find 7% of the new bill, so we're going to multiply 17 by .07 to get $1.19, and add it to the $17, making the final bill $18.19. You could also multiply $17 by 1.07 to get your final total without the extra step in the middle, but only do that once you're comfortable with the math.
Pls give brainiest
Recall the Maclaurin expansion for cos(x), valid for all real x :

Then replacing x with √5 x (I'm assuming you mean √5 times x, and not √(5x)) gives

The first 3 terms of the series are

and the general n-th term is as shown in the series.
In case you did mean cos(√(5x)), we would instead end up with

which amounts to replacing the x with √x in the expansion of cos(√5 x) :

4mph
0.4 x 7 mph =2.8 miles - distance run.
Let the required speed =S
[2.8 + 0.8S] / [0.4+0.8] =5, solve for S
S =4 mph - must walk to attain an average of 5 mph, or:
6 miles / 1.2 hours =5 mph