First binomial expression is A = (10r - 7).
Let's assume second binomial expression is B.
and third binomial expression is C = (93r + 12).
According to given question, A - B = C.
To find B, we can subtract C from A such that;
B = A - C
B = (10r - 7) - (93r + 12)
Distributing negative sign and removing parentheses;
B = 10r - 7 - 93r - 12
Combining like terms;
B = (10r - 93r) + (-7 -12)
B = (-83r) + (-19)
B = -83r -19
Hence, second binomial expression would be B = (-83r -19).
