R - 33 = 7 r = ?

if you can please give me an explanation cause i don't know how to do this at all.​

What is the first step of an indirect proof of a number that is divisible by two

Si la base de un triángulo isósceles mide 70 m y el ángulo opuesto a ésta mide 58°; entonces ¿cuánto mide la altura de dicho triángulo? a) 21.87 m. b) 40.01 m. c) 43.74 m. d) 63.14 m.

I’m stuck on this equation, anyone got the answer?