I don't think it’s “equal blame”.
We are told that God told Adam don’t eat of the fruit. Eve tells the serpent they’re not to eat of the fruit, or touch the tree - an addition God didn’t tell Adam.
Adam probably told Eve what God told him, adding the don’t even touch the tree on his own. This addition provided an opening for the serpent. In raising the question I’d wager Eve touched the tree for a second and waited to see what happened. When nothing happened she probably felt emboldened to eat of the fruit.
It also says they their eyes weren’t opened until Adam ate of it. Probably for the same reason - he didn’t see anything happen when she ate of it and felt safe enough to partake himself.
The blame is 70 / 30. Adam added to what God said (probably with good intentions - telling her not to even touch the tree will help avoid the temptation or something), didn’t rebuke the serpent (man was given dominion over all the creatures), and directly disobeyed God by eating of it himself.