Tolong bantuanya………..​

6.U3 = 18 = a + 2b …. (i)

U8 = 43 = a + 7b … (ii)

Eliminasi a

a + 7b = 43

a + 2b =`18 -> dikurangi

hasil : 5b = 25

b = 5

Substitusi pers (i)

a + 2b = 18

a + 2 x 5 = 18

a = 8

Panjang tali semula

S15 = n/2 x (2 x a + (n-1) x b)

= 15/2 x (2 x 8 + (15 – 1) x 5)

= 15/2 x (16 + 70)

= 15/2 x 86

= 645 cm

7.Agus = a

Bambang = b

Dika = c

a : b = 3 : 5 = 6 : 10

b : c = 2 : 1 = 10 : 5

a : b : c = 6 : 10 : 5

Jumlah uang Agus dan Dika

= (6 + 5)/(6 + 10 + 5) . 840.000

= (11/21) . 840.000

= Rp 440.000,00