Step-by-step explanation:
The total mammals = 314
Number of mammals in US = 63
Number of foreign mammals = A
Total mammals = Number of mammals in US + Number of foreign mammals
314 = 63 + A
subtract 63 from both sides:
314 - 63 = 63 - 63 + A
251 = 0 + A
A = 251
Hence, the number of foreign mammals is 251 (option B)