If you were to make both x's equivalent, you'd have to multiply the first equation by 2 to get rid of the coefficient, 1/2. However, you'd have to multiply 2 onto -8 as well, therefore the equation would turn into x - 16 = 18. That is not equivalent to x - 8 = 18.
You're pretty close. It's all in the details.
A. Correct.
B. Correct.
C. Sign error in the boxed answer. -(-0.5) = 0.5
The graph shows c ≈ 1.855. If a is more than that and decreasing, area is increasing. The sign of dA/dt will be positive. (Compare to D)
D. Units are not shown. Numerical value is correct.
After 5 tests, her average was 88. To have a seven-test average of 90, the total must be:

Her average after 5 tests was 88. Her total score on the 5 tests is:

Subtract:

Find the average by dividing by 2:

Her average must be 95
<h2>19.</h2><h3>Given</h3>
- window width and height are in proportion to building width and height
- window width and height are 11 in and 18 in, respectively
- building height is 108 ft
<h3>Find</h3>
<h3>Solution</h3>
The proportional relation can be written as
... (building width)/(building height) = (window width)/(window height)
Multiplying by (building height) gives
... (building width) = (building heigh) × (window width)/(window height)
... (building width) = 108 ft × (11 in)/(18 in)
... building width = 66 ft
<h2>21.</h2><h3>Given</h3>
- map distance = 6.75 in
- map scale = 1.5 in : 5 mi
<h3>Find</h3>
<h3>Solution</h3>
The distances are in proportion, so
... (map distance) : (actual distance) = 1.5 in : 5 mi
Multiplying by (5 mi)/(1.5 in)×(actual distance), we have
... (5 mi)/(1.5 in)×(6.75 in) = (actual distance) = 22.5 mi
Answer: 20 ;)
Step-by-step explanation: