b=9,a=12
Step-by-step explanation:
I solved by substitution:
b = 3/4a Ā ---> plug this into the other equation
a + b = 21 Ā is now Ā Ā a + 3/4a = 21
Reduce: 7/4a = 21
a = 12
Now solve for b:
b=3/4a is now b=3/4(12)
b=9
step-by-step explanation: