Question 1021176
{{{B=M+4}}}
.
.
{{{B-17=3(M-17)))
.
.
Substituting,
{{{M+4-17=3M-51}}}
{{{M-13=3M-51}}}
{{{-2M=-38}}}
{{{M=19}}}
Then,
{{{B=19+4}}}
{{{B=23}}}