we can determine the value of this number by setting an equation
the sum of the number and 7, multiplied by 3, is equal to 8 plus the number.
making x= the unknown number, we can say:
3(x+7) = 8 + x
now we can distribute the 3 and solve for x
3x+21 = 8+x
2x+21=8
2x= -13
x = -6.5
hope this helped