7b:
c= 15(9) + 18
c= 135 + 18
c+ 153
8:
"1.) Let x be the number of batches of dough and y be the number of dozen of cookies. So, the points of this function are (5, 7.5) and (7, 10.5). Fnd the slope of the line by using the slope formula m = (y2 - y1)/(x2 - x1), where (x2, y2) and (x1, y1) are points on the line:
m = (y2 - y1)/(x2 - x1) = (10.5 - 7.5)/(7 - 5) = 3/2
Write the equation in slope-intercept form, which is y = mx + b, where m is the slope and b is the y-intercept. You just found the slope as 3/2 or 1.5, so the equation so far is y = 1.5x + b. Now solve for b by substituting one of the points for x and y into the equation. I'll use point (5, 7.5):
y = 1.5x + b (substitute 5 for x and 7.5 for y)
7.5 = 1.5(5) + b
7.5 = 7.5 + b
0 = b
Therefore, the equation is y = 1.5x + 0 or simply y = 1.5x.
2.) If there are 12 batches of dough, then x = 12. Use the equation:
y = 1.5x = 1.5(12) = 18 dozen cookies
3.) 12 batches of dough make 18 dozen cookies and there are 12 cookies in a dozen, therefore 12 batches of dough makes 18*12 = 216 cookies."