Experts/ace/trusted /geniuses mee plz

inside angles need to equal 180

180-75-40 = 65

now the question mark and 65 need to equal 180

180-65 = 115

 answer is 115

i can't see the picture : /

because linear equations are a lot simpler than quadratics equations, and linear equations formula is a lot easier to memorize. that's why i think they're harder.