Mr. Lukic has $50 in his wallet, he gives $10 to Ms. Ferrando to pay for his lunch, he gives $3 to each of his three favorite nephews, and Ms. Sanchez pays Mr. Lukic $7 to buy her a book. How much money does Mr. Lukic have in his wallet at the end of the day?

Lukic starts off with $50, he gives $10 to Ms. Ferrando. 50 - 10 = 40. He’s left with $40 after this exchange. He gives $3 to three people. 3 x 3 = 9. 40 - 9 = 31. He’s left with $31. Ms. Sanchez pays him $7 to buy her a book.
We do not add nor subtract 7 from the answer as when it’s given it is spent immediately. There’s no point in adding 7 then subtracting it.

He is left with $31.

The answer for this question is 80

You didn’t put the necessary image to solve the question : p