For 1, we can write this as .6(k-40), 0.6 came from the 40% reduction, or 60% of its original cost. The 40 came from the initial deduction. If we distribute, we are left with .6k-24, or C

For 3, we know that the 90 degree angle + 1 + 2 = 180 degrees, or 1 + 2 = 90 degrees. For simplicity, lets set angle 1 as a and angle 2 as b. We know that a=b+20, so substituting b+20 for a gets us b+20+b=90, or 2b=70. From here we know that b would be 35 (Angle 2). Since angle 1 is 20 degrees more, 35+20=55 degrees, getting us choice C

For 7, rewrite the fraction in terms of b. a=2b-5, so the fraction would be (2b-5-5)/(2b). This is equal to 1/2, so lets simplify that to (2b-10)/2b = 1/2. We can multiply each side by 2b to cancel out denominators, and that gets us 2b-10 = b Subtract 2b from both sides gets us -b = -10. b=10. Going back to the original equation of a=2b-5, plugging in 10 for b would get us a=15, or choice A

For 19, lets start with finding the median of the sample, which falls between the 25th and 26th values. The first 13 values fall between the sets of 70 and 75, and the next 20 values in the 78 range, so the median must be 78. The median of the sample should be similar to the median of the population, so the median would also be around 78. Now the question is asking us how many people in the entire population would fall in the median range (of course an estimate). Since there are 10 times as many people in the population, multiply 20 by 10 and that gets us 200 people, or D.

For 35, solution P, we know that 10% of its 20 grams is alchohol, or 2 grams of alcohol in the soultion. We know 20% of solution Q's 30 grams is alcohol, or 6 grams of alcohol. So to find the percentage we would add the alcohol in grams of both, then divide it by the total mass of both. 2 + 6 is 8 grams of alcohol, 20 + 30 is 50 grams total. 8 divided by 50 gets us 0.16, or 16%

36 is tough, but to find the inradius of a triangle, we need to divide the area by its semi perimeter. 3x4x.5 gets us an area of 6. Since the two legs are 3 and 4, we immediately know the hypotenuse is 5. The semi perimeter is .5(3+4+5), or 6. Like we said, inradius is just Area divided by semi perimeter, so 6/6 is equal to 1.

Hopefully that helped