
To find short base $ b $ use formula:
$$ m = \frac{ a + b } { 2 } $$After substituting $m = 8.8\, \text{cm}$ and $a = 9.5\, \text{cm}$ we have:
$$ 8.8\, \text{cm} = \frac{ 9.5\, \text{cm} + b } { 2 } $$ $$ 8.8\, \text{cm} \cdot 2 = 9.5\, \text{cm} + b $$ $$ 9.5\, \text{cm} + b = 17.6\, \text{cm} $$ $$ b = 9.5\, \text{cm} + 17.6\, \text{cm} $$ $$ b = 27.1\, \text{cm} $$