Question

How many atoms are $s{p}^2$ hybridised in 7-ethyl-3-nonen-2,5,8-tricarboxylic acid?

Answer 1

All three carbon of three $-COOH$ are $s{p}^2$.
Three oxygen, one in each $-COOH$ are $s{p}^2$.

Both C-3 and C-4 carbons are $s{p}^2$.