tolong jawab soal no 18 yaa,, beserta cara nya yaa,,

diketahui
U1 = 90
U2 = 96
U3 = 102

b = U2 - U1 = 96 - 90 = 6
a = U1 = 90

ditanyakan U10
U10 = a + 9b = 90 + 9(6) = 90 + 54 = 144 cm
jadi tumpukan 10 kursi = 144 cm
jawaban C