"Your tea is tasty."
Translation:התה שלכם טעים.
Because תה is masculine - it's just something you have to remember.
If you think it's feminine because it ends in ה: It's true that a ה ending usually indicates a feminine word, but there are exceptions, so the ending is not a guarantee of gender. But what can help you remember the gender here is that תה is pronounced with an "e" vowel while usually feminine forms that end with ה will end with an "a" vowel.
You probably think it's plural because of טעים. No, it's singular. There are other adjectives that end in ים that are singular - נעים (pleasant), מדהים (amazing), מקסים (charming), מרשים (impressive) and so on. The plural for tasty is טעימים, so you add the plural ending, just like the other adjectives I listed.