Question

are these triangles similar?

write a similarity statement.
$\triangle \square \sim \triangle \square$

Explanation:

Step1: Find missing angle of $\triangle DFE$

Sum of angles in triangle is $180^\circ$.
$\angle D = 180^\circ - 98^\circ - 50^\circ = 32^\circ$

Step2: Find missing angle of $\triangle STU$

Sum of angles in triangle is $180^\circ$.
$\angle U = 180^\circ - 98^\circ - 50^\circ = 32^\circ$

Step3: Match congruent angles

$\angle D = \angle S = 32^\circ$, $\angle F = \angle T = 98^\circ$, $\angle E = \angle U = 50^\circ$

Step4: State similarity by AA criterion

Triangles have 3 congruent corresponding angles, so they are similar.
$\triangle DFE \sim \triangle STU$

Answer:

yes
$\triangle DFE \sim \triangle STU$