Let A = number of humans and B = number of horses
And we know
A + B = 74 → B = 74 - A (1)
2A + 4B = 196 (2)
Sub (1) into (2)
2A + 4(74 - A) = 196 simplify
2A + 296 - 4 A = 196
-2A + 296 = 196 subtract 296 from both sides
-2A = -100 divide both sides by - 2
A = 50 = humans
74 - 50 = 24 = horses