Idon’t know how to do this can someone

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

Which term best describes the association between variables a and b? no association a negative linear association a positive linear association a nonlinear association a scatterplot with an x axis labeled, variable a from zero to ten in increments of two and the y axis labeled, variable b from zero to one hundred forty in increments of twenty with fifteen points in a positive trend.

Measures of the angle of r, 31 s (x+4) t (3x+9)