Find the value of X When 6-3x=5x-10x+6

The triangles are similar. what is the value of x? x=

White shapes and black shapes are used in a game. some of the shapes are circles. while the rest are squares. the ratio of the number of white shapes to the number of black shapes is 5: 11. the ratio of the number of white cicrles to the number of white squares is 3: 7. the ratio of the number of black circles to the number of black squres is 3: 8. work out what fraction of all the shapes are circles.

What adds to be the bottom number but also multiplies to be the top number with 8 on the bottom and 15 on top