<span>In math notation, we've done this: z = (X - μ) / σ = (940 - 850) / 100 = 0.90
where z is the z-score
X is Vivian's score (940)
µ is the mean (850)
σ is the standard deviation (100)
As you may know, in a normal distribution it's expected that about 68% of all observations will fall within 1 standard deviation of the mean, 95% will fall within 2 standard deviations, and 99% will fall within 3 standard deviations.
940 lie before the first standard deviation, in which 16.5% is above it
since 940 is 0.9 from the mean and 0.1 from the first standard deviation
so above it is 17.5 % = 0.175 or about 0.18 </span>
The amount of money, b, is $140.
Standard form (which I assume is what they want you to turn these into) is y=mx+b.
12x-5y=20 is y=2.4x-4.
Subtract 12x from both sides, -5y=-12x+20.
Multiply both sides by -1, 5y=12x-20.
Divide both sides by 5, y=2.4x-4.
y=x+4 is already in standard form- I'm not quite sure what to do.
3x+y=3 is y=-3x+3.
Subtract 3x from both sides, y=-3x+3.
x=-y+3 is y=-x+3
Ad y to both sides, y+x=3.
Subtract x from both sides, y=-x+3.
12 x 12 = 144, 144 x 3 and then subtract 5 to get 427
90-73=17
answer：17 hahahaaha
