Step-by-step explanation:
1st digit is 1 number (1)
2nd digit is (3,4,5) so it's 3 numbers
third digit is (6,7,8,9) is it's 4 numbers
last 7 digits is 10 (0,1,2,3,4,5,6,7,8,9)
multiply
1*3*4*10=120
so answer is 120 phone numbers
Answer:
f(g(x)) = 15x³ - 5
Step-by-step explanation:
how confusingly described.
let me try and summarize what I understood :
f(x) = 3x² - 5
money earned when baking x cookies.
g(x) = sqrt(5x³)
the amount of cookies baked in x hours.
f(g(x)) now calculates how much money she earns when baking for x hours.
it is basically very simple : instead of f(x) we have f(g(x)), so g(x) is used as argument/variable in f instead of just plain x.
therefore,
f(g(x)) = 3×(sqrt(5x³))² - 5
with x now representing the baking hours, but f(...) calculating the overall money earned, by implicitly (!) calculating the amount of cookies baked in that time and taking that result automatically to calculate the earned money.
let's simplify this a little bit more.
f(g(x)) = 3×(sqrt(5x³))² - 5 = 3×(5x³) - 5 = 15x³ - 5
20b + 18s < = 150 (thats less then or equal)