Question

Find the value of 'x'. [3 MARKS]

(i) $4x+5=25$

(ii) $x-2\frac{1}{3}=5\frac{1}{2}$

(iii) $(7x+8)÷7=8$

Answer 1

Each Option: 1 Mark

(i) $4x+5=25$

$\Rightarrow 4x=25-5$

$\Rightarrow 4x=20$

Divide by 4 on both sides,

$4x÷4=20÷4$

$x=5$


(ii) $x-2\frac{1}{3}=5\frac{1}{2}$

$\Rightarrow x-\frac{7}{3}=\frac{11}{2}$(Taking LCM of 1 and 3 )

$\Rightarrow \frac{3x-7}{3}=\frac{11}{2}$

$\Rightarrow 3x=\frac{11}{2}\times 3+7$

$\Rightarrow 3x=\frac{33+14}{2}=\frac{47}{2}$

$\Rightarrow x=\frac{47}{6}=7\frac{5}{6}=7.833$

(iii) $(7x+8)÷7=8$

$\Rightarrow \frac{7x+8}{7}=8$

$\Rightarrow 7x=8\times 7-8=56-8=48$

$\Rightarrow x=\frac{48}{7}=6\frac{6}{7}=6.86$