решите уравнения:10к-к=702 , 4j+5j+j=1200 , 6t+3t-t=6400 с проверкой

1) 10к-к=7029к=702к=78k=702:9=782)4j+5j+J=120010j=1200j=120j=1200:10=1203)6t+3t-t=64008t=6400t=800t=6400:8=800