Answer
$ŷ=3891-296x_1+0.552x_2$
The coefficient for $x_1$: if the concrete’s slump increases by 1 inch and 7-day strength remains constant, then the 28-day strength will decrease by 296 psi, on average.
The coefficient for $x_2$: if the 7-day strength increases by 1 psi and concrete’s slump remains constant, then the 28-day strength will increase by 0.552 psi, on average.
Work Step by Step
Given above.
