1) 1 3/4 hr first mowing
13 total mowings
5 minutes less each mowing
in 12 mowings, time reduced by 5 min/ea
(5min*12mowings)=50min tolal min saved by 13th
convert hrs to minutes:
1 3/4hr = 60min + 45min=105min
(105min, 1st mow)-(5*12min saved, 13th mow)
= 45 minutes taken by 13th mowing

2) [(3+2/3) + (-5 + -3/4)]/[(7+3/4) + (-1 + -1/8)]
[(3+2/3-5-3/4)]/[(7+3/4-1-1/8)]
[-2 + 2/3 - 3/4]/[6 + 3/4 - 1/8)]
[-2 + 4/12 - 9/12] / [6 + 12/16 - 2/16]
[-2 + -5/12] / [6 + 10/16]
[-24/12 + -5/12] / [96/16 + 10/16]
[-29/12] / [106/16]
[-29/12] * [16/106]
[-29/3] * [4/106]
[-29/3] * [2/53]
[-29*2] / [3*53]
[-58] / [159]

4) 2^2 + 4(x + -6) = 4 – 7(5x – 9) + 6x -37
4+ (4x – 24) = 4 + (-35x + 63) + 6x -37
4x – 20 = 67 – 29x – 37
4x = 20 + 67 -29x -37
4x = 87 – 29x – 37
4x + 29x = 87 – 37
33x = 50
33x/33 = 50/33
x = 50/33
x = 1 17/33

3) I don’t have the cumulative formula; it isn’t especially nice as I remember it. However, this is what I got for the amount of money paid for the phone:

(375 * .85) is what you pay after the 15% discount
(375 * .05) is the amount of 5% tax on the full phone price
( (375 *.85) *.05) is the amount of 5% tax on the discounted amount
NOTE: In part it depends upon which value you pay tax on

If the full amount is taxed, you pay the following for the phone:
(375 * .85) + (375 * .05)

If you are only taxed for the discounted amount:
(375 * .85) + ( (375 *.85) *.05)