3 subtracted by 7 times a number

Need 50 will mark brainliest answer. find the lengths of all the sides and the measures of the angles.

Ahypothesis is: a the average squared deviations about the mean of a distribution of values b) an empirically testable statement that is an unproven supposition developed in order to explain phenomena a statement that asserts the status quo; that is, any change from what has been c) thought to be true is due to random sampling order da statement that is the opposite of the null hypothesis e) the error made by rejecting the null hypothesis when it is true

Could someone me with this question i’ve been stuck on it for 20 minutes