Answer: Robert should serve 3 for tea, 9 for lemonade, and 4 for water.
Step-by-step explanation:
Since you don't know how many friends are drinking lemonade or tea, you should give them variables.
x = amount of friends drinking tea
3x = amount of friends drinking lemonade
We already know how many are drinking water, so there's no need for a variable.
Then, make an equation:
x + 3x + 4 = 16
Simplify:
4x + 4 = 16
Isolate the variable by subtracting 4 from both sides:
4x = 12
Isolate the variable by dividing both sides by 4:
x = 3, so 3 friends are drinking tea
3x = 9, so 9 friends are drinking lemonade
Double check the work by replacing the variables with their actual numbers:
3 + 9 + 4 = 16
Simplify:
16 = 16
Therefore, the answer is correct.
