ANSWER
![|FG| = 19 \: units](https://img.qammunity.org/2020/formulas/mathematics/high-school/opmhdt7t0sqgl6mplxvj8bjzzv3jrsk2q2.png)
Step-by-step explanation
Since the altitude, |GJ| bisects the base of the triangle, it follows that, the triangle is an isosceles triangle.
This implies that,.
![|FG|=|GH|](https://img.qammunity.org/2020/formulas/mathematics/high-school/2athttb55i67y5ut8evaa3g715jz24t1d3.png)
In terms of x, we have the equation.
![5x - 6 = 3x + 4](https://img.qammunity.org/2020/formulas/mathematics/high-school/mjewqn7tp317p557wj45nlqrd57rm24jus.png)
We now group like terms to obtain,
![5x - 3x = 4 + 6](https://img.qammunity.org/2020/formulas/mathematics/high-school/90pd367clpqq9z3m7yf970n7gd6wfnf2zz.png)
This implies that,
![2x = 10](https://img.qammunity.org/2020/formulas/mathematics/high-school/725v21fytsu4474hd1g6bs9nmpaie9n71b.png)
Let us divide through by 2 to get,
![x = 5](https://img.qammunity.org/2020/formulas/mathematics/high-school/q47q2r4ttysyvhwrvmu4tvjt4greotllkp.png)
We can see from the diagram that,
![|FG|=5x-6](https://img.qammunity.org/2020/formulas/mathematics/high-school/4rw9wnsawpvp73tm8wdqp322lmvx06b6su.png)
We substitute x=5 to get,
![|FG|=5(5)-6](https://img.qammunity.org/2020/formulas/mathematics/high-school/e5ygxx9cvu2cuqviwa6huyy3gg35uordrg.png)
This simplifies to,
![|FG|=25-6](https://img.qammunity.org/2020/formulas/mathematics/high-school/5q31mt1l9vnbwue86hy7vz29se69za6una.png)
![|FG|=19 \: units](https://img.qammunity.org/2020/formulas/mathematics/high-school/otw6tk8q3erfohbsfuhpm62rff26jazaxu.png)