The points P, Q, R and S all lie on the same line segment, in that order, such that the ratio of PQ : QR: RS is equal to 1:4:1. If PS = 18, find QR.

what is the answer to this

m∠5 + m∠3 = m∠1   is true.

m∠5 + m∠6 = 180 is true

m∠2 +m∠3 = m∠6   is true

m∠2 +m∠3 +m∠5 = 180   is true

for this case we must apply distributive property to the following expression:

the distributive property states that:

then, when applying the property we have to multiply the -2 for each term within the parenthesis: