Question 565034
If the triangles are similar the ratio {{{height/base}}} is the same, so we write the proportion
{{{x/15=6/4}}}
{{{x/15=6/4}}} ---> {{{4x=6*15}}} (equating cross products)
{{{4x=6*15}}} ---> {{{4x/4=6*15/4}}} (dividing both sides by 4)
{{{4x/4=6*15/4}}} ---> {{{x=22.5}}} simplifying/performing indicated operations