What is the variable of 7m + 3​

M isn't it?

Step-by-step explanation:

7m+3

(move seven to the other side)

m=7-3

(7-3=4)

m=4

5=812a+9+3

step 1: simplify both sides of the equation.

5=812a+9+3

5=(812a)+(9+3)(combine like terms)

5=812a+12

5=812a+12

step 2: flip the equation.

812a+12=5

step 3: subtract 12 from both sides.

812a+12−12=5−12

812a=−7

step 4: divide both sides by 812.

812a /812 = -7/812

a= -1/116

so the answer is

a=   -1/116

i think it might be a but you might want a second opinion