Simplified:
kx + x² + 3x + 3k
Answer:
let required no be x

by doing crisscrossed multiplication

42=7x
dividing both side by 7

6=x
therefore x=6
therefore value of remaining no.is 6
x= morning
y = afternoon
x + y = 10
x=10-y
5x + 6y =57
5(10-y) +6y =57
50-5y +6y =57
y=7
x=10-7 =3
check 3*5 = 15, 7*6 = 42, 42 + 15 = 57
3 morning practices
Best option would be either B or C
If it is a triangle it would be 149