No she doesn't have enough money. All you do is multiply 8.60 by .2 which come out to 1.72 and 8.60 plus 1.73 which equals 10.33 so she needs 33 more cents tone able to tip 20%.
Inverse property of multiplication.
The horizontal stretch is the correct answer. A period is the distance on the x-axis that it takes for the tangent or cotangent function to repeat itself. Stretching it out horizontally will lengthen that distance and therefore change the period.
Let be be Beth, bi be Bill, and e be edie. Then:
1/be + 1/bi +1/e=1/12
1/bi + 1/e=1/15
10/be +10/bi +10/e+5/be+5/bi=1
Solve for be, bi, and e
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7:35 would be the ratio hope this helps! :))