Question 904646
from view of gold
90*0.9=0.75*(90+x)
81=67.5+0.75*x
81-67.5=0.75*x
13.5=0.75*x
x=18
check
90*0.9=0.75*(90+x)
90*0.9=0.75*(108)
81=81
ok

or from view of silver
1*y+0.1*90=0.25(90+y)
1*y+9=22.5+0.25y
1*y-0.25y=22.5-9
0.75y=13.5
y=13.5/0.75
y=18