Jawabanmu

2014-06-09T18:32:19+07:00
4x + 3 = 21 - 2x
4x + 2x = 21 - 3
6x = 18
x = 3

panjang sisi = 4x + 3 = 4.3 + 3 = 12 + 3 = 15 cm