Let the number of girls be g and the number of boys be b.
b = 3g
Class average = class score/class size = 17
17 = (class score) / 3g + g
68g = class score
Class score = girls score + boys score
Girls average = girls score/g
girls score = 18g
68g = 18g + boys score
boys score = 50g
Boys average = 50g/3g
= 16.7
So the left side has a common denominator of 3. The 6x, -2x, and 8 can all go over a single 3. (6x-2x+8/3). Simplify the x's to get 4x. Now both sides have to be multiplied by 3 to get rid of that fraction. Then you just have 4x+8=24. Subtract 8 from both sides to get the x's alone, then divide both sides by 4 to get x alone. I have a picture to help.
75% of the repair bill is 53.25
0.75x = 53.25
x = 53.25 / 0.75
x = 71 <== total cost of the bill
what's it look like if like this |__ right /_ acute \__ obtuse
Answer: $58.33 (Rounded bc it ends up in becoming a decimal)
Explanation: Let's make an equation for this problem. We know that if she works 3 hours for $25, 3*2=6 with 1 hour leftover. We can substitute those 6 hours for 2 sets of the 3 hours, giving us $50 so far. For the last hour, we have to divide 25 by 3 because it's only 1 hour instead of 3, meaning she'll get paid a third of the original pay rate. 25/3 equals 8.33333333334, so we'll just round that to 8.33, since it's cash. 50+8.33=$58.33. So, you'd earn 58 dollars and 33 cents for working for 7 hours.
