How do i solve this algebra problem? (5-a)divided by (a+7)=1/4 with 1,2,3, as solution set

I'm not sure what you mean by a "1,2,3, as solution set." Here is how I would solve the equation.

(5-a)/(a+7) = 1/4

Multiply both sides by (a+7).

5-a = (1/4)(a + 7) = a/4 +7/4

Subtract 5 from both sides and combine numerical terms

-a = a/4 + 7/4 -5 = a/4 + 7/4 - 20/4 = a/4 -13/4

Subtract a/4 from both sides to get all "a" terms on one side.

-a -a/4 = -5a/4 = - 13/4

Multiply by -4 to get rid of negative and divisor.

5a = 13

a = 13/5 = 2 3/5 = 2.6

I hope this helps. Thanks for asking.