Question 316906
{{{a+(a+d)+(a+2d)+(a+3d)=50}}}
1.{{{4a+6d=50}}}
.
.
.
{{{a+3d=4a}}}
2.{{{a=d}}}
Substitute into eq. 1,
{{{4d+6d=50}}}
{{{10d=50}}}
{{{highlight(d=5)}}}
.
.
{{{highlight(a=5)}}}
.
.
(5,10,15,20)