#### Answer

a) B U C = {x | x $\leq 5$}
b) B n C = {x | -1 $\lt x \lt 4$}

#### Work Step by Step

a) B union C means that numbers that are in either B or C are included, therefore, anything less than four from B, and anything from -1 up to, and including, 5 from C. These sets combine to include anything from negative infinity up to, and including, 5.
b) B intersect C means that only numbers in both B and C are included, therefore you can only use numbers as high as (but not equal to) 4 due to set B, and you can only use numbers as low as -1 because of set C.