How can i prove a triangle is equilateral without knowing any lengths or widths ?

Use sigma notation to represent the following series for 9 terms.

Idon't want to fail summer school.the probabilities of contamination in medicine capsules due to the presence of heavy metals and different types of microbes are given in the table.the probability of capsule b having microbial contamination is (the same as, greater than, less than) the probability of capsule d having it.

Solve the equation for x. 50(4x + 12) = 200