Question

Form the algebraic expression for the following statements:
a) Twice a number when decreased by $7$ gives $45$.
b) Two- fifths of a number added to $9$ gives $30$.

Answer 1

a) Let the number be $x$.

Therefore, twice the number $=2\times x=2x$

Now, twice the number when decreased by $7=2x-7$

Hence, twice a number when decreased by $7$ gives $45=2x-7=45$

Thus, the required algebraic expression is $2x-7=45$

b) Let the number be $y$.

Therefore, two- fifths of a number $=\frac{2}{5}\times y=\frac{2}{5}y$

Now, two- fifths of a number added to $9=\frac{2}{5}y+9$

Hence, two- fifths of a number added to $9$ gives $30=\frac{2}{5}y+9=30$

Thus, the required algebraic expression is $\frac{2}{5}y+9=30$