Solve using substitutuion

(question 1)
2x - 7y = -2
2x + y = 14

(question 2)
8x - 7y = 17
-x + y = -3

Lems1. the following data set represents the scores on intelligence quotient(iq) examinations of 40 sixth-grade students at a particular school: 114, 122, 103, 118, 99, 105, 134, 125, 117, 106, 109, 104, 111, 127,133, 111, 117, 103, 120, 98, 100, 130, 141, 119, 128, 106, 109, 115,113, 121, 100, 130, 125, 117, 119, 113, 104, 108, 110, 102(a) present this data set in a frequency histogram.(b) which class interval contains the greatest number of data values? (c) is there a roughly equal number of data in each class interval? (d) does the histogram appear to be approximately symmetric? if so, about which interval is it approximately symmetric?

Which coefficient matrix represents a system of linear equations that has a unique solution ? options in photo*

For the inequality |c| < |d| to be true, which of the following must be true?