If Zinzi gives x bricks to Chika, Chika ends up with 2+x bricks while Zinzi ends up with 10-x.
But Chika now has 3 times as many bricks as Zinzi, so 2+x=3(10-x)=30-3x.
Add 3x to each side of the equation: 2+4x=30, then take 2 from each side: 4x=28, so x=7.
Zinzi gives 7 bricks to Chika, so ends up with just 3 bricks, while Chika now has 9, which is 3 times as many as Zinzi.