a) using prime factorization (dividing with a prime factor until everything is a prime number, then multiplying the prime numbers by each other once), u can calculate their lcm
122=2x61
15=5x3
834=2x3x139
then multiply the prime factors once,
2x3x5x61x139= 254,370
b) i’m assuming that u solve the equation first bc u didnt put any commas
42-12-16=14
3-92+20=-69
do prime factorization
14=2x7
-69=-23x3
multiply the factors
-23x7x3x2=-966