Question 369697
Let C be the age of the china plate, G the age of the glass plate.
1.{{{C+G=16}}}
.
.
{{{(C-4)=3(G-4)}}}
{{{C-4=3G-12}}}
2.{{{C-3G=-8}}}
Subtract eq.2 from eq. 1,
{{{C+G-C+3G=16-(-8))}}}
{{{4G=24}}}
{{{G=6}}}years
Then from eq. 1,
{{{C+6=16}}}
{{{C=10}}}years