AMO 2027 Grades 6-7 SET 9 - Self-study Question 11

Mrs. Tan made some tarts. 1/4 of them were lemon tarts and the rest were strawberry tarts. After 210 lemon tarts and 5/6 of strawberry tarts were sold, she still had 1/5 of the tarts left. How many tarts did Mrs. Tan make at first?