Algebra 1

$\frac{-1+\sqrt 7}{4}\approx0.4$
Multiply both sides by the denominator of the left side. $\frac{x}{2+\sqrt 7}=\frac{3-\sqrt 7}{4}$ $x=\frac{(3-\sqrt 7)(2+\sqrt 7)}{4}=$ $\frac{6+3\sqrt 7-2\sqrt 7-7}{4}=$ $\frac{-1+\sqrt 7}{4}\approx0.4$