Page 52 - 新思维数学学生用书8 样章

2.5 Constructing and solving equations

c y − 10 = 1 (add 10 to both sides) y − 10 + 10 = 1 + 10
4 4
(simplify) y =
4
(multiply both sides by 4) y = × 4

(simplify) y =

d 6y + 2 = 4y + 18 (subtract 4y from both sides) 6y − 4y + 2 = 4y − 4y + 18

(simplify) y + 2 = 18

(subtract 2 from both sides) y + 2 − 2 = 18

(simplify) y =

(divide both sides by ) y =

(simplify) y =

3 For each learner
i write an equation to represent what they say x − 3 = 15
ii solve your equation to find the value of x. 2
The first one has been started for you. x − 3 + 3 = 15 + 3
2
a x =
2
My sister is 15 years old.
My Dad is x years old. Half of x = × 2
my Dad’s age minus 3 is the
same as my sister’s age. x =

b

My brother is 12 years old.
My Mum is x years old. One-
third of my Mum’s age plus 1 is
the same as my brother’s age.

c

My Aunt is 30 years old.
My Gran is x years old.
One-quarter of my Gran’s
age plus 9 is the same as
my Aunt’s age.

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