To solve for the variable "a" in the first equation:

4/7 = 8 + 2a/21
Multiply both sides by 21 to get rid of the fraction:
4 3 = 8 21 + 2a
12 = 168 + 2a
Subtract 168 from both sides:
12 - 168 = 2a
-156 = 2a
Divide by 2:
a = -78

To solve for the variable "a" in the second equation:

5/12 = 30/44 + 7a
Multiply both sides by 44 to get rid of the fraction:
5 44 = 30 12 + 44 * 7a
220 = 360 + 308a
Subtract 360 from both sides:
220 - 360 = 308a
-140 = 308a
Divide by 308:
a = -140/308
a = -70/154
a = -35/77