Question

d * 7 = mod 120
How to calculate the value of d?

Answer 1

\(d \times 7 = \text{mod} 120\implies\)
\(d \times 7\div 7 = \text{mod} 120\div 7 \implies\)
\(d = \text{mod} 120\div 7 \)

Answer 2

77. 8*11

Answer 3

77. 8*11

Answer 4

@thoutu why are you linking a pdf on model? Typically, mod means modulo or modulus. In computer science, it is usually a reference to the remainder. There is a reasonable description here:
http://en.wikipedia.org/wiki/Modulo_operation

If the asker meant something else, then it is probably in the wrong section.