I need to solve equation in mod .what to do?

I want to find d from 7*d mod 40 =1.

I need to solve equation in mod.what to do ?

I do

Syms d

Eqn=Mod(1,40)==7*d;
Sold=solve(Eqn,d)

But Answer is

1/7

Answer 1

[Torsten]

http://www.mathworks.com/matlabcentral/fileexchange/32856-system-of-linear-congruences/content/lincon.m

Best wishes

Torsten.

[Sakunrat Jaejaima]

Thank you so mush.

Answer 2

[Steven Lord]

For a system this small? Brute force works fine.

d = 0:39;
d(mod(7*d, 40) == 1)

[Sakunrat Jaejaima]

Thank you so mush.