I have done this type of example 5 times. I know I have the regression equation right. But I don't know what i'm doing with the second part. Please help! Listed below are systolic blood pressure...

I have done this type of example 5 times. I know I have the regression equation right. But I don't know what i'm doing with the second part.

Please help!

Listed below are systolic blood pressure measurements​ (in mm​ Hg) obtained from the same woman. Find the regression​ equation, letting the right arm blood pressure be the predictor​ (x) variable. Find the best predicted systolic blood pressure in the left arm given that the systolic blood pressure in the right arm is 80mm Hg. Use a significance level of 0.05.

Given that the systolic blood pressure in the right arm is 80mm​ Hg, the best predicted systolic blood pressure in the left arm is     mmHg