加数 is read as かすう (kasuu) and means addend.
かすう
kasuu
じゅうりょくかそくどていすう
gravitational constant
かんぞうかちょうかんすう
tempered distribution
ひかすう
augend
かにゅう
joining (a club, organization, etc.)
かこう
manufacturing
かそく
acceleration
くわわる
to be added to
かがいしゃ
perpetrator
かじゅう
weighting (in averaging)
くわえる
to include
か
Canada
かてん
adding points