"You are strong."
Although many people say that Anda is formal, it is not necessarily polite. People usually use honorific terms instead of pronouns if they want to sound polite. The hierarchy pf 2p pronouns in daily Jakartan Indonesian is like this:
situ = informal-disrespectful
lu, lo = informal-impolite (denotes intimacy if used between friends)
kamu = informal-polite (in Jakarta this pronoun is romantically charged, e.g. used between lovers, but not so in other regions)
the person's name = informal-affectionate (parents-children, wife-husband, etc.)
Anda = formal-neutral (in business meetings, or in formal speeches)
Kinship terms (bapak "father", ibu "mother", kakak "older sibling", adik "younger sibling", mas "young man", mbak "young woman) = formal-polite
Using Anda is sometimes deemed as a passive-aggressive behavior. Use kinship terms instead if you're not sure. Estimate the person's age or social position when you first meet them. If their age is just slightly different from yours, use mas/mbak (both are borrowed from Javanese). If their age is seemingly much older, use bapak/ibu instead. Adik is commonly used towards children.