You are given that angle GHJ is a complement of angle RST and angle RST is a supplement of angle ABC. Let the measurement of angle GHJ be x°. What is the measure of angle ABC?

GHJ = x

GHJ (or x) is a compliment of RST....complimentary angles, when added = 90...so RST = (90 - x)

RST is a supplement of ABC....supplementary angles, when added = 180...so ABC = (180 - RST)...and remember RST = (90 - x)

so ABC = 180 - (90 - x)
             = 180 - 90 + x
             = 90 + x....or 90 + GHJ <===