Question 307928
The probability of hitting the inside rectangle is equal to the area of the inside rectangle over the area of the outer rectangle.
The area of a rectangle is 
{{{A=LW}}}
The area of the inner triangle is
{{{Ai=(x+5)(x+3)}}}
The area of the outer triangle is
{{{Ao=(2x+5)(x+3)}}}
.
.
.
{{{P=Ai/Ao=((x+5)(x+3))/((2x+5)(x+3))}}}
{{{P=((x+5)cross(x+3))/((2x+5)cross(x+3))}}}
{{{P=(x+5)/(2x+5)}}}