F(g(x)) means you take the g function and put it into x in the f function. He took the function and put it into the g, which was the incorrect order. He should have had this: 
Olivia is half the age of her brother, Adam. Olivia's sister, Ava, is twice as old as Adam. Adam is 4 years old. How old is each
2 answers:
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Answer:
see explanation
Step-by-step explanation:
A = πr² ← r is the radius and r = d ← d is the diameter
Hence
π ( d)² = A, that is
= A ( multiply both sides by 4 )
d²π = 4A ( divide both sides by π )
d² = ( take the square root of both sides )
d =