What is the mistake in this equation?

2 - 5 = 7

i am giving away a free 50 points for a yt video and this is like the most simple answer. if you can tell me the mistake, you'll get the 50 points and i'll mark you brainiest.

Mr and mrs smith buy tickets for themselves and their four children. the cost of an adult ticket is ? 6 more than the adult ticket. the total cost of the six tickets is ? 40.50 work out the cost of an adult ticket. in your working let c be the cost of the child ticket and a be the cost of the adult ticket.

Ana drinks chocolate milk out of glasses that each holdof a liter. she has of a liter of chocolate milk in her refrigerator. 10 how many glasses of chocolate milk can she pour?

What is the geometric mean of 3 and 7? a) square root of 21 b) 2 square root of 6 c) 2 square root of 7 d) 21