Answer:
180 grams
Explanation:
Mitchell has to use more coffee than usual for two reasons: First, he's making a larger pot than usual (15(15left parenthesis, 15 cups rather than 10)10)10, right parenthesis. And second, he's using the Arabica coffee, which requires 20\%20%20, percent more coffee for the same strength.
2
Instead of brewing \blue{10}10start color blue, 10, end color blue cups, Mitchell wants to brew \red{15}15start color red, 15, end color red cups, which means he has to use \dfrac{\red{15}}{\blue{10}}=\purple{1.5}
=1.5start fraction, start color red, 15, end color red, divided by, start color blue, 10, end color blue, end fraction, equals, start color purple, 1, point, 5, end color purple times more coffee.
3
As his friend said, Mitchell also has to use \pink{20\%}20%start color pink, 20, percent, end color pink more coffee than usual, so he'll have to multiply the amount of coffee by \green{1.2}1.2start color green, 1, point, 2, end color green, or \green{120\%}120%start color green, 120, percent, end color green.
4
The total amount of coffee he has to use is 100100100 grams \times×times \purple{1.5} \times \green{1.2} = 1801.5×1.2=180start color purple, 1, point, 5, end color purple, times, start color green, 1, point, 2, end color green, equals, 180 grams.