In parallelogram STUV, opposite angles are equal, and adjacent angles sum to 180°.<br><br>Given ∠SVU : ∠TSV = 3 : 7.<br>Let ∠SVU = 3 units and ∠TSV = 7 units.<br>Since SVU and TSV are adjacent angles in the parallelogram, 3u + 7u = 10u = 180°, so 1 unit = 18°.<br><br>∠STU is opposite ∠SVU, so ∠STU = ∠SVU = 3 &times; 18° = 54°.<br><br>Final Answer: 54°