Question

Seja a E R. A média aritmética entre a, 8, 2a, 9 e (a + 1) é 6,8. Qual o valor de a?

Answer 1

$\frac{a+8+2a+9+(a+1)}{5}=6,8\\\frac{a+2a+a+1+8+9+}{5}=6,8\\\frac{4a+18}{5}=6,8\\4a+18=6,8\times 5\\4a=34-18\\4a=16\\\Rightarrow a = \frac{16}{4}=4$