Определение подобных т-ков .Найдите х,у,z

Решите задачу:

$1\\\\ \frac{BC}{B_1C_1}= \frac{x}{A_1C_1} \\ \\ \frac{28}{21}= \frac{x}{18} \\\\ x= \frac{28*18}{21}= 24$

$2 \\\\ \frac{N_1K_1}{NK}= \frac{2}{1} \ \ \to \ \ k=2 \\ \\ x=k*MN=2*4=8 \\ y=k*NK=2*7=14 \\ z=k*MK=2*6=12 \\$

$5\\\\ P_{MQR}=2+5+4=11 \\ \\ k= \frac{P_{M_1Q_1R_1}}{P_{MQR}} = \frac{110}{11}=10 \\ \\ x=k*QM=10*2=20\\y=k*QR=10*5=50 \\ z=k*MR=10*4=40$

$6 \\\\ A_1B_1=6k; \ \ \ B_1C_1=4k; \ \ \ A_1C_1=3k; \\ \\6k+4k+3k=91 \\ 13k=91 \\ k=91:13 \\ k=7 \\ \\ x=6k=6*7=42 \\ y=4k=4*7=28 \\ z=3k=3*7=21$