Question

Robert and Susan's mother is 160cm tall.

Answer 1

Robert is a boy, so you only need the formula for a boy’s predicted height.

father’s height=x
fathers height=180
so, x=180

mother’s height=y
mother’s height=160
so, y=160

plug in x=180 and y=160 into the formula.
0.4(x+y)+42
0.4(180+160)+42

use GEMDAS to simplify.

G(Groupings)

0.4(180+160)+42
0.4(340)+42

M(Multiplication)
0.4(340)+42
136+42

A(Addition)
136+42
178

The predicted height of Robert when he is an adult is 178 cm.