Question

a x 50% + 1/5 x a + a x 1,8 + 108 = 123   

Answer 1

\(a\times50\%+\dfrac{1}{5}\times a+a\times1,8+108=123\)
\(a\times\dfrac{1}{2}+\dfrac{1}{5}\times a+a\times\dfrac{9}{5}=123-108\)
\(a\times\left(\dfrac{1}{2}+\dfrac{1}{5}+\dfrac{9}{5}\right)=15\)
\(a\times\dfrac{5}{2}=15\)
\(a=15:\dfrac{5}{2}\)
\(a=6\)