Solve each system of equations below by the substitution method. and show your work. x+y=143x+2y(y-5)=21

Iam so stuck. what is the worked out answer for this question?

An alien has just landed from the planet, iksnimak. he would like to leam how to add two fractions when thedenominators are the same. write a paragraph that explains to our alien friend, in your own words, the detailsabout how to add the fractions, how to change the result to a mixed number, and how to reduce the fractionpart. use this problem as your example: the two fractions are 5/8 & 7/8

Which one is true about the hexagons ?